EVALUATION OF INTAKE LIMITING AGENTS IN A SELF-FED...

EVALUATION OF INTAKE LIMITING AGENTS IN A SELF-FED DRIED

DISTILLERS’ SUPPLEMENT

A Thesis

by

JOEL DUSTIN SUGG

Submitted to the Office of Graduate Studies of

Texas A&M University in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

Chair of Committee, Jason E. Sawyer Committee Members, Andy D. Herring William E. Pinchak Tryon A. Wickersham Head of Department, H. Russell Cross

August 2013

Major Subject: Animal Science

Copyright 2013 Joel Dustin Sugg

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ABSTRACT

Response to range supplementation is in part driven by level of supplement

consumed and amount of associated variation. In order to evaluate intake limiting agents

in a self-fed dried distillers’ grain supplement (DDG), heifers (n=59) in Trial 1 were

offered an ad libitum amount of sorghum × sudangrass hay as well as DDG containing

either no limiter (CON), monensin (185 mg/kg; MON), or one of six additional limiters

alone or in combination with monensin (185 mg/kg, +M). Evaluated treatments and

initial rates consisted of sodium chloride (NACL, 10%), urea (UREA, 2%), sodium

bicarbonate (LIME, 1.68%), DL-malic acid (MLAC, 3%), calcium propionate (CAPR,

3%), and sodium bicarbonate plus urea (LIUR, 1.68% + 2%). Supplement intake was

recorded daily and limiters were evaluated over three rates of inclusion, each for a

duration of 14 d, on the basis of intake level, intake variation (cumulative stability), and

rate of intake change over time (temporal stability). Data was analyzed as a 7 × 2

factorial initial 7 days of each period were removed to avoid acclimation influence. A

baseline period was observed to ensure no inherent differences were detected. Within the

initial rate period, limiter affected OM intake (P = 0.02) as consumption was reduced by

NACL (P < 0.01) and tended to be lower when limited by MLAC (P = 0.14) and LIUR

(P = 0.11). Neither monensin (P = 0.86) nor a limiter × monensin interaction were

present. Cumulative stability was indicated that heifers consuming NACL (P < 0.01) and

CAPR (P < 0.01) consumed supplement with greater regularity than did CONT.

Monensin (P = 0.75) and monensin × limiter (P = 0.76) did not influence intake stability.

Temporal stability was unaffected by limiter (P = 0.43), monensin (P = 0.69), or

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monensin × limiter (P = 0.93). When rate of inclusion was 2 × initial rate, intake was

affected by limiter (P < 0.01) with observations similar to the initial period. No

monensin (P = 0.49) or interaction (P = 0.27) effect was present. Cumulative stability

was unaffected by limiter (P = 022), monensin (P = 0.39), or interaction (P = 0.86).

Temporal stability was increased with monensin (P 0.05) and an interaction resulted in

an increased rate of supplement intake change in CONT when monensin was included.

When supplement included limiters at 4 × the initial rate, Effects on intake and

cumulative stability by limiter were the only significant responses. Intake of LIUR,

NACL, and MLAC were reduced relative to CONT while NACL was consumed with

greater regularity. Trial 2 was conducted to further compare sodium chloride and DL-

malic acid as limiting agents. Each were included in a self-fed DDG supplement offered

to steers (n=60, mean initial BW = 191 kg) at identical rates (8%, 16% 24%, and 32%)

in addition to monensin (66 mg/kg). Within each rate, MLAC reduced supplement

intake more effectively than NACL while cumulative stability and temporal stability

measures were similar among limiter and only deviated from control levels at lower

rates.

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TABLE OF CONTENTS

Page

ABSTRACT………………………………………………………………………... ii

TABLE OF CONTENTS…………………………………………………………... iv

LIST OF FIGURES………………………………………………………………... v

LIST OF TABLES………………………………………………………………… vii

CHAPTER I INTRODUCTION AND REVIEW OF LITERATURE…………….. 1

Intake variation….....……...…............................................................. 1 Limitation of intake………………………………………...……... 8 Dried distillers’ grains…………………………………………….. 15 Metaphylaxis and implants…………………………………….….... 19 CHAPTER II ASSESSING THE EFFECTIVENESS OF INTAKE

CONTROL AGENTS IN A SELF-FED SUPPLEMENT BASED ON DRIED DISTILLERS’ GRAINS……………………................…. 22

Introduction…………………………………………….………..… 22

Materials and Methods….………………………………………… 23 Results and Discussion……………………………………………. 29 Conclusion………………………………………………………… 78

CHAPTER III COMPARISON OF SODIUM CHLORIDE AND DL-MALIC

ACID AS INTAKE LIMITING AGENTS IN A SELF-FED DRIED DISTILLERS’ GRAIN SUPPLEMENT........................…... 82 Materials and Methods……………………………………………... 82 Results and Discussions…………………………………………...... 87 Conclusion….………...…………………………………………....... 98

CHAPTER IV EVALUATION OF STACKED PRODUCTION TECHNOLOGIES ON ADG OF CALVES GRAZING SMALL

GRAIN WINTER PASTURES…..………………………….……. 99 Materials and Methods………………………………………….….. 99 Results and Discussion……………………………………………... 105 Conclusion………………………………………………………...... 116

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LITERITURE CITED……………………………………………………………. 118

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LIST OF FIGURES

Figure Page

1 Cumulative stability of supplement OMI by treatment during the initial rate period……………………………………………………………… 36

2 Hay OMI by treatment during the final 7 d of the initial rate period…………. 41 3 Supplement DMI by treatment during the final 7 d of the initial rate period… 43 4 Cumulative stability of OMI by treatment during the intermediate rate period. 47 5 Temporal stability of supplement OMI by treatment during the final 7 d of

the intermediate rate period…………………………………………………… 50 6 Hay OMI by treatment during the final 7 d of the intermediate rate period…. 52 7 DMI by treatment during the final 7 d of the intermediate rate period……….. 53 8 Supplement OMI by treatment during the final 7 d of the final rate period….. 56 9 Cumulative stability of supplement OMI by treatment during the final 7 d

of the final treatment period…………………………………………………… 58 10 Temporal stability of hay OMI by treatment during the final 7 d of the final

rate period……………………………………………………………………... 61 11 Regressed DMI cumulative stability by percentage of limiter inclusion……… 94 12 Regressed DMI temporal stability by percentage of limiter inclusion………… 96 13 Regressed DMI of sorghum × sudangrass hay by percentage of limiter

inclusion……………………………………………………………………… 97 14 Standing forage (kg/dm/ha) in paddocks expressed as means within collection

date…………………………………………………………………………. 112 15 Standing forage mass relative to mean BW of steers by dietary treatment…… 113 16 Available forage by diet and day expressed in kg DM/100 kg BW………….. 114

17 Nutritive values of paddocks expressed as means within collection date……. 115

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LIST OF TABLES

Table Page

1 Limiting agent inclusion rate by period in a self-fed dried distillers’ grain supplement fed to yearling heifers………………………………………........ 25

2 Initial rate period nutrient composition of treatment in a self-fed dried

distillers’ grain supplement and sorghum × sudangrass hay………………… 26

3 2 × initial rate nutrient composition of treatments in a self-fed dried distillers’ grain supplement and sorghum × sudangrass hay…………………. 27

4 4 × initial rate nutrient composition of treatments in a self-fed dried distillers’ grain supplement and sorghum × sudangrass hay……………………………. 28

5 Period 1 intake of hay and supplement, and supplement intake variance measures of a self-fed dried distillers’ grain supplement fed to growing beef heifers…...……………………………………………………………….. 33

6 Period 2 intake of hay and supplement, and supplement intake variance measures of a self-fed dried distillers’ grain supplement fed to growing beef heifers…………………………………………………………………….. 45

7 Period 3 intake of hay and supplement, and supplement intake variance measures of a self-fed dried distillers’ grain supplement fed to growing beef heifers…………………………………………………………………….. 54

8 Regression coefficients1 of OMI values over entire 14 d periods…………….. 62

9 Regression coefficients1 of OMI values over last 7 d of periods……………… 64

10 Regression coefficients1 of indexed OMI values over entire 14 d periods……. 66

11 Regression coefficients1 of indexed OMI values over entire last 7 d of periods…………………………………………………………………………. 67

12 Regression coefficients1 OMI cumulative stability values over entire 14 d of periods…………………………………………………………………………. 69

13 Regression coefficients1 OMI cumulative stability values over last 7 d of

periods………………………………………………………………………… 70

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14 Regression coefficients1 of indexed OMI cumulative stability over 14 d periods………………………………………………………………………. 71

15 Regression coefficients1 of indexed OMI cumulative stability over last 7 d of periods………………………………………………………………………. 72

16 Regression coefficients1 of OMI temporal stability values over 14 d

periods………………………………………………………………………. 74 17 Regression coefficients1 of OMI temporal stability values over last 7 d of

Periods………………………………………………………………………. 75

18 Regression coefficients1 of indexed OMI temporal stability over 14 d periods……………………………………………………………………….. 76

19 Regression coefficients1 of indexed OMI temporal stability over last 7 d of

periods………………………………………………………………………. 77 20 Regression coefficients1 of sorghum x sudangrass OMI by treatment……… 79

21 Regression coefficients1 of indexed sorghum x sudangrass OMI by treatment…………………………………………………………………….. 80

22 Nutrient composition of treatments1 and sorghum x sudangrass hay by

week………………………………………………………………………… 85 23 Intake, cumulative stability, and temporal stability of supplement intake by

limiter and inclusion rate……………………………………………………. 89 24 Regression coefficients1 for intake, intake variance, and time stability……. 92

25 Mean daily hay intakes (kg) by percentage of limiter inclusion…………….. 96

26 Regression coefficients1 of indexed DM and OM intakes………………….. 98

27 Composition of hand-fed energy supplement fed to steers grazing oat pastures (as-fed)……………………………………………………………... 101

28 Descriptive criteria for subjective health evaluation………………………... 104

29 Mean BW and ADG by treatment of steers grazing winter oats……………. 106

30 Mean BW and ADG by treatment interactions of steers grazing winter oats (kg)……………………………………………………………………... 107

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31 Nutrient composition by day of winter oat pastures………………………… 116

32 Weather data expressed as means within collection period…………………. 116

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CHAPTER I

INTRODUCTION AND REVIEW OF LITERATURE

Necessity for supplementation of livestock diets is driven by the magnitude of

difference between nutritional value and quantity of available forage relative to nutrient

level required to achieve production goals. Consumption of diets based on dormant

warm season perennial grasses often generates a need for supplemental crude protein

and, on occasion, energy to assist in both intake and digestibility of the forage base

(DelCurto et al., 1990). In addition to protein and energy, vitamins and other nutrients

may be offered at predetermined target amounts to mediate nutritional deficiencies.

Similarly, supplemented feeds may be used as carriers for ionophores and/or antibiotics

in which delivery of appropriate dosages are contingent upon an animal consuming at

least a target amount of feed (Kunkel et al., 2000). Overconsumption will increase cost

of supplementation and in the case of protein, animals are unable to efficiently utilize

excess supply. Deviation from desired intake levels can lead to variance from the

anticipated response to a supplemental regimen. Ideally, supplemented nutrients should

be included and consumed in amounts only necessary to meet physiological demands

within circumstance and without excess.

Intake variation

Supplement intake by grazing animals is often quantified by dividing supplement

disappearance by number of animal days. As a result of evaluating intakes as a mean

within a group, estimation of individual intake as well as intake variation are commonly

unreported. This is common in a large portion of previously

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published literature.

Individual intake variation has previously been reported as coefficient of

variation (CV) for intake, proportion of animals in a group which consume minimal or

no supplement (non-feeders), and proportion of animals within a group that consume a

target amount of supplement (Bowman and Sowell, 1997). Intake variation in feedlot

settings has commonly been assigned a residual value which is derived from the

difference in daily intake relative to average daily feed intake over a period (Stock et al.,

1995). Factors contributing to variation include form and palatability of supplement,

mode of delivery, feed allowance, and multiple aspects of social interaction (Bowman

and Sowell, 1997). To date, most studies estimating intake variation of free choice

supplements to grazing animals have been conducted with molasses based blocks and

liquid supplements.

Supplement form

Supplemental nutrients may be derived from a variety of sources which include

ethanol by-products, oilseed by-products, animal by-products, forages, minerals, and

grains. Diversity of supplement form includes meals, loose mixes, forages, cubes,

blocks, or liquids. Physical form of feed has been identified as a factor influencing

intake variation (Bowman and Sowell, 1997).

In an effort to describe differences in behavior and intake associated with form of

supplemental protein, Garossino et al. (2003) assigned gestating beef cows either

molasses blocks or liquid molasses. At least 70% of cows selected to receive liquid

molasses consumed supplement on a daily basis whereas attendance to block supplement

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ranged from 40 to 80%. No differences were detected in mean daily DM intake though

standard deviation (SD) of daily intake was higher for the block treatment. Additionally,

rate of consumption and was higher when supplement was in liquid form though

duration of feeder attendance was reduced. These measures could directly relieve social

dominance issues by increasing the proportion of time the bunk is unoccupied. Neither

group of animals achieved the targeted mean daily intake. Before initiation of this trial,

all cows were corralled with access to the block supplement which should eliminate

novelty as a factor influencing variation of block intake in these observations.

Mulholland and Coombe (1979) provided wethers grazing wheat stubble with

mineral blocks, urea-containing mineral blocks, liquid molasses, and urea-containing

liquid molasses. Mean CV’s were lowest for mineral blocks and highest for liquid

molasses (44% vs. 64%) whereas values for the urea containing supplements were

intermediate at 47% and 58% for blocks and liquid, respectively.

In multiple experiments evaluating intake and intake variation, Dixon et al.

(2003) offered various supplements to grazing heifers. In Experiment 1, groups were

assigned one of four treatments: 1) restricted amount of cottonseed meal (CSM), or ad

libitum access to 2) liquid molasses containing 74 g/kg urea (M8U), 3) salt and urea-

containing loose mineral mix (LMM), or 4) molasses blocks containing 62 and 99 g/kg,

respectively, salt and urea (BLOCK). Intake variation expressed as CV among heifers

within group after 10 weeks was highest for BLOCK (83%), intermediate for LMM

(71%), and lowest for M8U and CSM (26% and 28%, respectively). Additionally, all

heifers assigned CSM and M8U treatments consumed some supplement. Proportions of

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non-feeders were 4% and 19% for LMM and BLOCK, respectively. These experiments

suggest that both variation in supplement consumption and the proportion of non-

consumers a herd are expected to be greater when supplements are offered in block

form. In Experiment 2, heifers were offered ad libitum access to one of four liquid

molasses supplements containing low amounts of urea (74 g/kg), high amounts of urea

(107 g/kg), monensin (120-180 mg/kg), or meat meal. No significant differences in CV

of supplement intake were detected among the four treatments. All heifers consumed

supplement with exception of 30% of those assigned molasses containing meat meal.

Ducker et al. (1981) measured individual variation of block supplement intake of

ewes from a wide range of environmental settings. Intake CV ranged from 46% to 231%

among 15 flocks. The overall percentage of ewes not consuming any supplement was

19%. These authors attributed differences in intake to ewe age, alternative feed

availability, and variation between flock locations.

Lobato and Pearce (1980) described influence of forage availability in relation to

block supplement intake. Approximately 1200 total grazing ewes at 5 locations were

offered molasses-urea blocks. After an initial 3 week period, 50% of ewes had consumed

no supplement, and were removed and confined to yards where they were provided

blocks and 350 g hay·ewe-1·d-1. After 3 weeks in confinement, percentage of non-feeders

measured 19% and those were retained for an additional period ranging from 2 to 4

weeks during which 88% of ewes consumed supplement. Overall individual intake of

supplement was highly variable on both pasture (100 to 400 g·ewe-1·week-1) and in

confinement (100 to 500 g·ewe-1·week-1).

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In a study of supplement and forage intake by ewes grazing native winter range,

Taylor et al. (2002) fed supplemental protein in pellet (27% CP) and block (29.3% CP)

form. Ewes receiving pelleted feed were group fed the wheat middling-soybean meal

based supplement at 114 g·ewe-1·d-1 whereas ewes assigned to the block treatment were

allowed ad libitum access. Mean consumption of the two treatments were 110 and 58

g·ewe-1·d-1 for the pellet and block supplements, respectively. Ewes receiving pelleted

supplement had fewer non-feeders relative to those receiving block (2% vs. 35%), fewer

individuals classified as having low-intake (5% vs. 10%), a higher proportion of animals

consuming 51% to 150% of the mean intake (83% vs. 27%), fewer animals consuming

excess supplement (10% vs. 28%), and a reduced CV of intake (32.0% vs. 99.5%).

Dove and Freer (1986) provided grazing lambs individually with sunflower meal

(SFM) in loose meal or pelleted form. Mean intake of pelleted SFM was higher (388 vs.

335 g·lamb-1·d-1) and CV was reduced (9.9% vs. 21.2%). Similarly, Beck (1993) fed a

self-limiting energy supplement to cattle grazing wheat pasture for four consecutive

years. In years one and two, supplement was fed in pellet form and in meal form in years

3 and 4. Calculated CV’s for individual supplement intake were 32% for years one and

two (pellet) and 42.6% for years three and four (meal).

Intake variation of oats, hay, and urea-containing molasses blocks fed to grazing

sheep was measured in multiple experiments by Lobato et al. (1980). Observed CV for

oat grain intake was slightly lower than that of hay (23.4% vs. 30.5%). Measure for

block intake was much higher at 143.6%. Mean intakes (g DM·hd-1·week-1) were highest

for hay and lowest for molasses-urea block.

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Tait and Fisher (1996) measured intake of a 1:1 salt-commercial mineral mix and

found wide ranges of intake by grazing steers (50 to 300 g·hd-1·d-1) with a mean intake

of 135 g/d and CV of 41%.

Collectively, these studies indicate that liquid supplements and dry feeds may

deliver nutrients to grazing livestock with reduced variability relative to blocks.

Delivery method

Providing supplemental nutrients to grazing livestock can be achieved by

delivering smaller amounts of feed intended for immediate consumption or by delivering

feed in bulk that is designed or formulated to be consumed over extended periods. Hand-

feeding a smaller portion allows for tighter control of daily intake but may increase

operational costs associated with necessity of frequent delivery (Sawyer and Mathis,

2001). Due to feed supply in lesser amounts, hand-feeding my elevate level of

competition and dominance issues leading to a higher proportion of non-feeders. These

occurrences are influenced by numerous factors which include amount of accessible

trough space, age of animals in the herd, and breed differences (Bowman and Sowell,

1997).

In contrast, self-feeding creates an opportunity to ameliorate costs by reducing

frequency of travel and labor (Sawyer and Mathis, 2001). Energy and mineral

supplements are especially suited for self-fed delivery since their efficacy is improved

when offered daily. Benefits of providing protein in self-fed form are not as predictable

due to flexibility in feeding frequency (Wallace and Parker, 1992; Huston et al., 1999).

Additionally, manipulation of grazing distribution may be achieved by strategic

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placement of stationary feeders (Bailey and Jensen, 2008). However, individual intake

variation is expected to be higher in animals consuming supplement with this method

(Bowman and Sowell, 1997).

Kendall et al. (1980) reported that heifers in confinement hand-fed a barley/SBM

cubed supplement had individual supplement intake variation (CV) of 31%, compared to

57% in those fed blocks of the same formulation. These results were confirmed in a

subsequent trial, where individual intake CV’s were higher for blocks than for cubed

supplement (82% vs. 55%, respectively).

Feed allowance

Feeding frequency may be drastically different depending on delivery method

(hand-fed vs. self-fed) and, as a result, influence of feed allowance on intake variation

must be considered. Schauer et al. (2005) reported no difference in CV values (28%) for

protein supplement intake when cottonseed meal was offered to mature grazing cows

daily and every sixth day (0.91 vs. 5.46 kg·hd-1·d-1). These data contradict observations

of decreased variation when feed allowance is higher (Huston et al., 1999). When

supplement is offered at identical daily rates, daily feedings will supply a smaller

amount of feed per delivery. Less frequent delivery will increase feed availability for a

period prior to depletion thereby decreasing competition and dominance issues. Schauer

et al. (2005) measured intake and intake variation at a single point in time in this study

and only a small portion of the population was observed. It is possible that the timing of

data collection in this case did not provide a true indication of variability.

8

Foot et al. (1973) observed decreases in CV (36% to 16%) of intake by ewes

when supplement allowance was increased from 100 to 453 g·hd-1·d-1. In evaluating

block consumption by ewes, Ducker et al. (1981) identified an increase in proportion of

non-feeders when mean flock consumption was lower and that the proportion decreased

as mean consumption increased. Kendall et al. (1980) quantified intake variation of ewes

provided low, intermediate, or high feed allowances offered in restricted, sufficient, or

excess trough space and found that CV for supplement intake was inversely related to

amount of supplement provided. Variability was further increased as trough space

allowance was reduced.

Limitation of intake

Intake limiting agents

Diet selection by an animal is a function of nutritional demand and sensory

acceptability of feed characteristics (Provenza, 1995, 1996 a,b). When provided with

supplemental nutrients, unregulated consumption will often exceed amounts necessary to

meet requirements. Supplemented nutrients generally make up a relatively small

percentage of a ruminant’s overall diet and level of necessary intake is likely reached

well before satiety signals are received from gut hormones and central nervous system

activity.

Sodium chloride is commonly used as a limiter of feed intake. Wide ranges

(0.7%, Meyer et al., 1955; 45%, Judkins et al., 1985) have been included in feedstuffs

with concentration adjustments occasionally needed due to increased tolerance (Kunkle

et al., 2000). When salt is included as a limiter, a greater intake reduction per unit of salt

9

inclusion is expected with dry feeds relative to liquids. In addition, pelleted supplements

diminish the effectiveness of salt as a limiter compared to loose mixes and feeds in meal

form (Kunkle et al., 2000).

Gypsum (CaSO4) has been successfully used to limit intake, and inclusion rates

to meet targeted intakes may be lower than levels of salt required to achieve the same

intake (Barrentine and Ruffin, 1958) though its use is less common due to considerations

of high sulfur content and risks of toxicity or polioencephalomalacia. Similarly, calcium

chloride has been used to effectively limit supplement intake when included at

concentrations lower (2.5% to 5.0%) than those shown to be effective for salt. However,

corrosive properties are a concern and excess calcium renders the ionic halide

undesirable in feeds not high in phosphorous content (Kunkle et al., 2000).

Animal fat (yellow grease) included at a level of 10% in a supplement of No. 2

corn to grazing steers limited daily supplement intake to 0.79% BW (Wise et al., 1965).

When salt was included in corn at levels to coincide with intakes of the fat-containing

supplement, salt levels were similar and ranged from 7 to 10%. One advantage of fat

inclusion is increased energy supply though difficulties associated with storage and

handling in cold weather along with scouring and possible decreases in forage digestion

are potential disadvantages. Wise et al. (1965) observed greater ADG and supplemental

conversion over the six month trial when supplement was limited by fat.

Jensen (1979) measured the efficacy of numerous limiting agents in a ground

corn supplement to cattle grazing irrigated pasture. In the first of multiple experiments,

limiters (as a percentage of supplement) corn starch (50%), dehydrated potatoes (100%),

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dicalcium phosphate (10%), and sodium tripolyphosphate (5%) were not effective at

maintaining intake of supplement below a level of 1.82 kg·hd-1·d-1 after brief periods of

adaptation. Another experiment utilized animal fat (7.5%, 10.0%, and 15.0%), sodium

hydroxide (1.0%, 1.5%, and 2.0%), phosphoric acid (3.0%, 4.0%, 5.0%, 6.0%, and

7.0%), and phosphoric acid plus monensin (3.0%, 5.0%, 6.0%, and 7.0% in addition to

110 mg per kg) and again found no significant differences in overall intake among

treatments (P < 0.05) with intakes generally increasing with animal adaptation. An

additional experiment was conducted using sodium hydroxide (1.0%, 1.5%, and 2.0%),

aluminum sulfate (4.0%, 6.0%, 8.0%, and 10.0%), ammonium chloride (2.0% and

6.0%), ammonium chloride plus ammonium sulfate (2.0% plus 6.0%), bone meal

(8.0%), calcium chloride (4.0%), and corn gluten meal (60.0%) as intake modifiers.

Sodium hydroxide at 2.0%, aluminum sulfate at 10.0%, and ammonium chloride at

either 2% or 6% constrained supplement intakes to target levels. A comparison of

aluminum sulfate plus monensin (5.0% and 10.0% plus 220 mg per kg), calcium

carbonate plus monensin (5.0%, 10.0%, and 15% plus 220 mg per kg), and magnesium

sulfate plus monensin (5.0% and 7.5% plus 220 mg per kg) suggested that all

combinations successfully limited supplement intake although number of days observed

were as few as three for some of these treatments. Measures of intake variation in this

study are not reported.

Urea is included in most liquid feed products and its capacity to limit intake has

been evaluated. Barker et al. (1988) fed a 3:1 urea/superphosphate blend in a grain

supplement fed ad libitum to steers consuming low quality hay. Concentration of the

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blend in the supplement was increased over a period of 20 weeks in 14-d intervals from

4% to 27%, resulting in a significant treatment effect on supplement intake with

reductions as high as 70% compared to stable intake of supplement containing a constant

inclusion of 2.67%.

Schauer et al. (2004) compared the effectiveness of three intake limiters in a

wheat middling based supplement offered in consecutive years to steers grazing native

prairie from June through October in North Dakota. Sodium chloride (16%), ammonium

chloride (3%) plus ammonium sulfate (2.25%), and calcium hydroxide (7%) were

included in the supplement which was also hand fed at a rate of .50% and 0.49% initial

body weight (BW) during year 1 and 2, respectively. Treatments were offered in pellet

(4.4 mm) form with the exception of the calcium hydroxide treatment which was fed in

meal form. Data were analyzed in 28 d periods to monitor possible interaction with

seasonal change. In year 1, no differences were detected in supplement intake which

averaged 2.69 kg DM·hd-1·d-1 or 0.64% BW. In year 2, anionic salts failed to limit intake

during the first two periods as intakes reached 2.05 and 2.55 kg·hd-1·d-1 compared to

hand-fed rates of 1.64 and 1.63. Among these limiters, calcium hydroxide was most

effective compared to other treatments during the first two periods. Steers assigned to

control in this study were used to measure performance differences due to

supplementation and did not receive supplement. Steers offered supplement without

limiter were hand fed at a rate of 0.50% initial BW. Therefore, efficacy of limiters

relative to unrestricted access of supplement is unknown. Intake of all limiter-containing

supplements increased relative to hand-fed intake over the trial and no treatment effects

12

were present during the last two periods. As a likely indication of acclimation to the

limiters, mean increase in supplement intake across both years from initial to final period

was 221%, 161%, and 202% for sodium chloride, anionic salts, and calcium hydroxide,

respectively.

Malic acid

Studies evaluating influence of the dicarboxylic organic acids fumaric acid and

malic acid in ruminant diets to date have primarily pertained to their role in

methanogenesis. Newbold et al. (2005) suggests that propionate precursors may function

as electron sinks competing with methanogens for ruminal H2. Published results have

highly variable, ranging from no effect (Beauchemin and McGinn, 2006; McCourt et al.,

2008) to reductions in methane production as high as 75% (Wallace et al., 2006). Use of

these propionate precursors to reduce methanogenesis may also influence feed intake.

Multiple studies present evidence of reduced CH4 emissions/day but not per kg DMI,

and attribute these findings to reductions in total DMI when diets contain various levels

of organic acids (McGinn et al., 2004; Beauchemin and McGinn, 2006; Molano et al.,

2008).

Foley et al. (2009) observed linear decreases in total DMI by including malic

acid in a supplement fed to heifers (P < 0.001) and steers (P = 0.002). When heifers

were subjected to 3 levels of malic acid inclusion (0%, 3.5%, and 7.5%), a linear

decrease was also observed in supplement (P < 0.001) and silage (P = 0.01) intake.

Malic acid inclusions of 0%, 2.5%, 5.0%, and 7.5% in supplement fed to steers

generated quadratic reductions to silage consumption (P = 0.003) and total DMI (P <

13

0.001). A tendency for a quadratic effect (P = 0.07) was observed for supplement intake.

In each case, DMI was affected by initial increment with no other reductions at

subsequent levels.

Wallace et al. (2006) observed intake of an ad libitum concentrate diet by lambs

of 0.3 kg and 0.2 kg lower relative to a control group (P < 0.10) when fed either 100g/kg

concentrate of fumaric acid or 117g/kg of encapsulated fumaric acid, respectively.

Similarly, Molano et al. (2008) observed reduced DMI when wethers were fed ground

lucerne with fumaric acid inclusions of 4%, 6%, 8%, and 10% of DM. Reductions in

DMI (kg/d) and CV’s for DMI relative to control were 0.04 and 5.94%, 0.27 and

18.18%, 0.21 and 19.28%, and 0.22 and 17.07%, respectively. These results appear to be

quadratic though polynomial contrasts were not reported.

Conversely, numerous studies have produced no evidence of malic acid influence

on feed intake (Kung et al., 1982; Martin et al., 1999; Montano et al., 1999, Carro et al.,

2006; Wang et al., 2009). However, these studies included organic acids at rates much

lower relative to other studies where effects were observed. Of these studies finding no

influence on voluntary intake, the highest inclusion rate was 2.66% DM (Montano et al.,

1999).

Monensin

Manipulation of rumen metabolism has been the focus of extensive research due

to possible performance increases associated with improved fermentation. Monensin

sodium is a commonly used feed additive ionophore (Schelling, 1984). A primary

advantage of feeding monensin is a shift in volatile fatty acid (VFA) production in which

14

propionate is increased at the expense of acetate (Richardson et al., 1976). As a result,

energetic efficiency is improved due to the role of propionate in both gluconeogenesis as

well as direct oxidation via the citric acid cycle. Schelling (1984) summarized monensin

influence on ruminants and classified its biological effects into modification of VFA

production, change in feed intake, change in gas production, modified digestibility,

protein utilization, rumen passage, and other effects.

Muller et al. (1986) provided results of multiple trials in which monensin was

included with a target consumption of 200 mg·hd-1·d-1 (actual 177 mg·hd-1·d-1) in self-

fed energy supplements to grazing cattle on various types of pasture. Supplements were

limited by salt and level of inclusion (5% to 36%) was adjusted to maintain desired

intake levels in each trial. Pooled data indicate that cattle consuming monensin had

higher average daily gain (ADG; P < 0.01) and consumed 18.2% less supplement than

control cattle. In addition, salt levels were lower and less frequent adjustments to salt

level in order to maintain intake were required in groups fed monensin. In the trials

included, means both minimum and maximum levels of salt required to maintain

targeted intakes were reduced by monensin inclusion by 49.6 and 30.4%, respectively.

These data indicate that monensin may serve as a limiter of supplement intake without

sacrificing gain performance.

Potter et al. (1986) observed similar effects when monensin (200 mg hd-1·d-1)

was fed in supplements to steers fed forage based diets in confinement. In trials where

feed intake was measured, pooled values for cattle fed monensin were lower (3.1%, P <

0.01) than for control groups. Improvements in ADG and feed:gain were also realized (P

15

< 0.01). Paisley and Horn (1996) reported monensin (165 mg/kg) reduced intakes of a

self-fed energy supplement by steers grazing wheat (P < 0.001; .64 and 2.29 kg·hd-1·d-1,

respectively). Catsaounis et al. (1980) top-dressed the feed of bulls with a mineral

supplement with or without monensin and observed reduced total daily feed intakes

(8.9%) by bulls consuming monensin. Weight gain and feed conversion were increased

(1.8% and 11.3%, respectively). Intake of corn-based supplement by finishing heifers on

ryegrass was 25% less (P < 0.05) when the supplement contained 66 mg/kg monensin

(Utley et al. 1978). No difference was observed in ADG between treatment groups.

Jensen (1979) found that supplement intake was only temporarily held to target levels

when monensin was included in a corn supplement at concentrations of 220 mg/kg,

330mg/kg, and 440 mg/kg. Intakes increased after cattle acclimated to treatments.

Dried distillers' grains

Supplements to grazed forage systems are provided to increase individual animal

performance and their value is estimated by the extent of increased production as a result

of improved nourishment. Due to relatively high crude protein and energy density levels,

dried distillers’ grains may be an ideal supplement to dormant warm season forages.

Roughly two-thirds of the protein content within DDG is undegradable (UIP, by-

pass) by ruminal microbes (NRC, 1996). Though lower levels of animal production may

be sustained from microbial crude protein alone, DDG as a supplement to grazing

ruminants has the capacity to facilitate higher levels of production by contributing a

considerable proportion of protein to the small intestine. MacDonald et al. (2006)

measured daily gains when an alternate UIP source was supplemented at a level to

16

provide the amount of bypass protein obtained from DDG. Results indicated that gain

response was only about 40% of that realized with DDG supplementation on growing

forages. Implications are that about one third of gain increases observed with DDG

supplementation may be due correcting microbial protein deficiencies.

As an added convenience, fat levels in DDG render the co-product a potential

supplemental energy source supplying 120% the energy value of corn. The fiber in DDG

is highly digestible and in combination with fat levels, increases value as a viable energy

source (Lodge et al., 1997). Conventional grain-based energy supplements have reduced

fiber digestibility of low and moderate quality forages when offered at levels up to 0.9%

BW (Chase and Hibberd, 1987). Due to removal of starch during production of

distillers’ by-products, reduced competition between amolytic and cellulolytic microbes

are expected, thus reducing the occurrence of negative associative effects.

Positive associative effects have been observed with use of supplemental DDG.

Neither inclusion of supplemental UIP using corn gluten meal nor fat via corn oil in a

supplement at levels contained within DDG resulted in observed ADG by heifers offered

a DDG supplement on bromegrass pastures (MacDonald et al. 2007). This indicates that

the combined attributes of proportional UIP of total crude protein and fat in DDG

contribute the uniqueness of DDG and its potential to provide performance increases in

grazing ruminants.

Numerous measures of performance increase and forage substitution are

available. Heifers consuming various forage qualities supplemented with DDG up to

0.95% BW had increased overall ADG and consumed less forage per unit increase of

17

DDG intake (MacDonald and Klopfenstein, 2004; Morris et al., 2006). Luepp et al.

(2009) fed increasing levels (up to 1.2% BW) of DDG to steers fed moderate quality

forage and observed linear decreases in hay OMI and linear increases in both DDG and

total OMI. Additionally, Loy et al. (2007) offered a DDG supplement both daily (0.4%

BW) and on alternate days (0.8% BW) to heifers consuming grass hay (8.0% CP) and

reported similar decreases in hay DMI and increases in total DMI.

From an economic perspective, value of DDG as a supplement can be derived

from the sum of values attributed to increased performance and reduction in forage

consumption. At the very least, DDG should be considered a viable option in selection

of a highly valuable forage supplement. Allocation of DDG worth between forage

replacement and animal performance is highly variable. In a trial by Morris et al. (2006),

89.1% of DDG value was attributed to improved animal performance with DDG

supplement to low quality forages being 3.3 percentage units higher than the value on

high quality forage (90.8% vs. 87.5%) when fed at identical rates. This result would be

consistent with expectations due to greater potential for nutritional mediation in lower

quality forage conditions. MacDonald and Klopfenstein (2005) grazed heifers on

bromegrass and estimated that DDG supplement worth was primarily a factor of forage

replacement (62.4%). In regards to DDG value partitioning, a portion of the

discrepancies between these two studies may be attributed to inconsistencies in assigned

value of grazed forage and higher rates of supplementation.

Market price of DDG is typically determined by the current price of conventional

protein and energy feeds, soybean meal and corn. Common estimates of cost relative to

18

corn range from 70% to 90% on a DM basis. These prices are suspended by costs of

processing that included drying but are lower than wet products due to reduced freight as

a result of deliverable dry matter.

Published intake ranges of DDG up to 1.0% BW are numerous; however,

estimates of unregulated DDG intake are elusive. Though demonstrations of forage

substitution have been reported at various supplement rates, limitations to dietary

inclusion exist due to sulfur concentration and, in the case of cattle fed in confinement,

issues with physically effective fiber (peNDF) and fat levels when used as the primary

energy source. Published rates of supplemental inclusions are as high as 3.6 and 3.5

kg·hd-1·d-1 for pasture and pen-fed studies, respectively (Griffin et al., 2009). Due to

difficulties associated with measuring forage consumption on pasture, estimates from

pen studies are primarily used to quantify forage intake as a response to supplement

intake.

Despite enhancement of supplement potential due to nutrient profile, wide

variances in concentration of other nutrients have been observed. Belyea et al. (1989)

stated that CP% of DDG can range from 27% to 35%. Mean concentrations and CV of

CP% (30.2%, 6.4%) and crude fat (10.9%, 7.8%) published by Spiehs et al. (2002) were

similar to estimates of concentration and variance reported by Belyea et al. (2004) who

sampled DDG over a five year period. These wide ranges may contribute to difficulty in

formulating supplements or estimating allowances to meet animal demands. Primary

sources of nutrient variation have not been positively identified. Belyea et al. (2004)

analyzed corn supply to an ethanol plant and reported no correlation between

19

components of corn and DDG thus suggesting that variation is likely not associated with

variability of nutrient profiles in sourced corn but instead inconsistencies in ethanol

processing.

Along with issues in nutrient variability, physical structure is a characteristic of

concern that may influence the application in feeding systems. Analysis of DDG particle

form identifies some properties of concern in effectively delivering the feed to grazing

animals (Rosentrater, 2006). Issues of binding in storage bins and bulk feeders are less

severe with dried products relative to wet feeds; however, residual moisture, fat

concentrations, and shape and structure of particles contribute to occasional issues

(Behnke, 2007). Coincidentally, attributes that yield DDG a desirable feedstuff also

complicates its potential to conform as a consistent pellet. Two of the primary examples

are reduced starch, which serves to bind particles, and a higher level of hydrophilic

content due to oils that reduce bonding capability (Behnke and Beyer, 2002).

Metaphylaxis and implants

Metaphylaxis

Metaphylactic antimicrobial therapy is a mass application practice intended to

mitigate risk and implications of disease outbreak within a group. Treatment is usually

administered upon arrival as cattle typically break within the first few days. Despite

costs of blanket treatments, mass drug application may be desirable due to possible

occurrences of subclinical illness or caretaker failure to identify symptoms (Nickell and

White, 2010). In a compilation of studies evaluating metaphylactic use in arriving feeder

cattle, Wileman et al. (2009) reported improved (P < 0.01) morbidity treatment and

20

mortality rates of 47% and 53%, respectively. This same analysis also reported an

improved ADG of 0.11 kg in cattle subjected to metaphylaxis compared to untreated

cattle. Step et al. (2007) evaluated single or multiple dose administration and observed

response to treatment was improved when cattle were dosed a single time but that bovine

respiratory disease morbidity was less severe when cattle were treated once on arrival

and a second time eight days later.

Implants

Anabolic growth promoting agents improve gain performance of stocker cattle in

a consistent manner by 10 to 15% and have the potential to increase response to

supplementation programs (Kuhl, 1997). McMurphy et al. (2009) measured influence on

ADG by multiple implant types with multiple supplements by steers grazing summer

pasture. Implantation generated increased ADG (7.7%, P < 0.01) over the entire 126-d

grazing period with no differences observed among implant types. Interaction of implant

and supplement type was not significant though steers consuming a dried distillers’

grain supplement had higher ADG relative to steers consuming cottonseed meal due to

increased energy utilization. Despite absence of this interaction in the presence of

increasing plane of nutrition, other studies suggest expectations of performance as

influenced by implantation should be expected to increase as quality and availability of

basal diet improve (Selk et al., 2006).

Sufficient evidence that DDG is a viable option for range supplementation to

grazing cattle is available in previous literature. However, there is uncertainty of

effective delivery methods other than hand feeding. Further evaluation of intake control

21

agents with an emphasis on novel intake limiters and their combinations with monensin

may lead to an increase in value of the by-product if its delivery to can be reliably

predicted.

22

CHAPTER II

ASSESSING THE EFFECTIVENESS OF INTAKE CONTROL AGENTS IN A

SELF-FED SUPPLEMENT BASED ON DRIED DISTILLERS’ GRAINS

All animal care and use procedures described in this protocol were approved by

the Texas A&M University Animal Care and Use Committee (AUP 2009-239).

Research was conducted at the Texas A&M AgriLife McGregor Research Center outside

of McGregor, TX during the winter of 2010/2011.

Introduction

Dried distillers’ grains can be provided to grazing cattle as a source of both

supplemental crude protein and energy from fat and highly digestible fiber (Lodge et al.,

1997; MacDonald et al., 2007). Numerous studies have documented intake and animal

performance responses using hand fed supplemental DDG at various consumption rates

(MacDonald and Klopfenstein, 2004; Morris et al., 2006; Luepp et al., 2009); however,

previous literature is void of efforts to quantify intake of supplemental DDG provided ad

libitum. Method of supplement delivery is expected to influence precision with which

nutrient mediation is achieved (Bowman and Sowell, 1997). Providing a supplement to

grazing cattle free choice will often result in higher variation in supplement intake and

thus diminish efficacy (Kendall et al., 1980). Therefore, value of DDG as a supplement

may be enhanced if methods to accurately control intake are identified.

Traditionally, sodium chloride has been included in range supplements for

purposes of intake restriction. Ranges of inclusion are wide and necessary formulations

have been as high as 45% (Judkins et al., 1985). Kunkle et al. (2009) noted that frequent

23

formulation adjustments may also be needed due to acclimation. Exploration of

alternative agents using criteria of intake and variation of intake are warranted. Muller et

al. (1986) found that inclusion of monensin in an energy supplement offered to cattle not

only served to limit intake, but also improved longevity of limiter effectiveness. With

this reasoning, our objective was to evaluate potential intake limiting agents included at

multiple rates both alone and in combination with monensin at in a self-fed DDG

supplement. Criteria of evaluation included supplement intake, variation in daily

supplement intake, and stability of supplement intake over time.

Materials and methods

Fifty-nine Angus-sired, weanling heifers (191 kg mean initial BW) were used to

evaluate the effectiveness of potential intake limiting agents with and without monensin

in a self-fed corn distillers’ grains (DDG) supplement. Heifers were stratified by

weaning weight and randomly assigned (2 heifers per pen) to pens equipped with four

Calan gates (American Calan, Inc., Northwood, NH). Each heifer was fitted with keys

enabling access to two Calan gate feed bunks, one containing chopped hay and the other

containing supplement. Initially, heifers were provided 1 kg/d of DDG and ad libitum

access to sorghum x sudangrass hay in the adjacent bunk until acclimated to the feeding

system and bunk assignments.

Following acclimation, heifers were provided with ad libitum access to DDG

and hay. Refusals of supplement were weighed each morning prior to feeding for four

days preceding application of treatments to determine baseline intake of DDG and hay

by each animal. Heifers were weighed on the first day that treatments were applied.

24

Treatments were randomly assigned to pen and bunk. Treatments were arranged

as a 7 X 2 factorial with 6 limiting agents plus a negative control offered alone or in

combination with monensin (185 mg·kg-1·suppl.-1). Limiting agents were: no limiter

(CONT), salt (NACL), urea (UREA), limestone (LIME), malic acid (DL-malic acid,

food grade, Baddley Chemicals, Inc., Baton Rouge, LA; MLAC), calcium propionate

(NutroCal, Kemin AgriFoods North America, Des Moines, IA; CAPR), and limestone

with urea (LIUR). Supplements were prepared in bulk each week by combining limiting

agent and DDG in a portable rotary mixer for a duration of at least five minutes and until

visual appraisal of consistent particle distribution was achieved. Treatments were

sampled from mixer immediately after manufacturing of each 45 kg batch and

composited within period.

Treatments were applied during three sequential experimental periods with

increasing rates of limiter inclusion among periods (Table 1). Period durations were 14,

15, and 13 days for periods 1, 2, and 3, respectively. Animals and treatments were not

re-randomized in subsequent periods to avoid the influence of novelty on consumption

responses. Additionally, rates were not randomized among periods to avoid creation of

aversions in earlier periods that would unduly influence responses in later periods. Thus,

rate and period were purposefully confounded, and data from each period were analyzed

separately to make comparisons among limiters within experimental periods.

25

Table 1. Limiting agent inclusion rate by period in a self-fed dried distillers’ grain supplement fed to yearling heifers (% inclusion in supplement, as-fed basis)

Treatment1,2

Item CONT NACL UREA LIME MLAC3 CAPR4 LIUR

Baseline Control 0 0 0 0 0 0 Period 1 Control 10 2 1.68 3 3 1.68 + 2 Period 2 Control 20 4 3.36 6 6 3.36 + 4 Period 3 Control 40 8 6.72 12 12 6.72 + 8

1Treatments were salt (NACL), urea (UREA), calcium carbonate (LIME), malic acid (MLAC), calcium propionate (CAPR), and calcium carbonate plus urea (LIUR). 2Treatments were fed alone or in combination with monensin (+M; 2.5%) 3Kemin AgriFoods North America, Inc., Des Moines, IA. 4Baddley Chemicals, Inc., Baton Rouge, LA.

All animals had continuous, ad libitum access to chopped sorghum x sudangrass

hay (Table 2). Hay availability was monitored daily during supplement feeding and

supplied on an individual basis when necessary. During each experimental period,

supplement refusals were weighed at 0700 daily. Supplement was then added to replace

disappearance from previous day plus 0.91 kg of additional supplement to ensure ad

libitum access. Every seventh day, accumulated refusals of both supplement and hay

were sampled and discarded then replaced with fresh feed to mimic weekly

replenishment of a bulk feeder in practice. Refusal samples collected every seventh day

were composited by animal and within period for DM and OM measure.

Samples of supplements, hay, and refusals of both were placed in a forced-air oven at

60ºC for 96 h to determine DM. Samples were ground to pass through a 1 mm screen of

a Wiley mill (Thomas Wiley, Laboratory Mill Model 4, Thomas Scientific Co.,

Philadelphia, PA) and analyzed for ash, NDF, ADF, and CP. Organic matter was

calculated from ash content of a 0.5 g sample placed into a muffle furnace (500º C) for 8

26

hours. Fiber content was estimated using ANKOM 200 Fiber Analyzer (ANKOM

Technologies, Inc., Macedon, NY). Crude protein values were derived using Dumas

combustion (Rapid-N-Cube, Elementar America, Inc., Mt. Laurel, N.J.). Nutrient

composition of treatments and hay by period are provided in Tables 2, 3, and 4.

Table 2. Initial rate period nutrient composition of treatment1,2 in a self-fed dried distillers’ grain supplement and sorghum x sudangrass hay.

Nutrient Item DM% OM% NDF% ADF% CP%

CONT 90.24 94.03 43.03 12.39 27.80 NACL 91.48 85.71 38.54 10.59 26.59 UREA 90.88 93.90 43.62 11.26 29.79 LIME 91.15 92.75 44.33 11.94 29.52 MLAC 91.19 94.82 43.64 12.39 27.61 CAPR 86.92 91.61 42.85 10.80 24.97 LIUR 90.36 93.27 46.18 13.70 28.74 CONT+M 90.90 94.06 43.54 10.44 27.80 NACL+M 91.34 85.21 41.07 9.99 27.78 UREA+M 90.11 94.25 41.63 11.56 23.90 LIME+M 89.84 91.89 42.94 12.47 31.30 MLAC+M 90.90 93.14 45.64 14.45 27.75 CAPR+M 91.34 92.58 39.41 12.02 27.22 LIUR+M 90.76 90.70 41.39 12.40 27.43 Hay 93.77 91.02 56.79 28.45 9.94 1Treatments were salt (NACL), urea (UREA), calcium carbonate (LIME), malic acid (MLAC), calcium propionate (CAPR), and calcium carbonate plus urea (LIUR). 2Treatments were fed alone or in combination with monensin (+M)

27

Table 3. 2 × initial rate nutrient composition of treatments1,2 in a self-fed dried distillers’ grain supplement and sorghum x sudangrass hay.

Nutrient

Item DM% OM% NDF% ADF% CP%


28

Within observation periods, calculated standard deviation of supplement intake

(cumulative stability), rate of change in supplement intake (temporal stability),

coefficient of variation of supplement intake, and daily hay intake were evaluated along

with direct measure of supplement intake. Temporal stability, or the directional change

in daily intake over time, was quantified by regressing individual intakes within period

using day as a first order predictor. After initial analysis, second-order regressions of

supplement intake on time were estimated for each heifer. The derivative of estimated

equations were set to zero and solved to determine a critical value of the predictor. A

secondary analysis was conducted of data including days after the mean critical value

Table 4. 4 × initial rate nutrient composition of treatments1,2 in a self-fed dried distillers’ grain supplement and sorghum x sudangrass hay.

Nutrient

Item DM% OM% NDF% ADF% CP%


29

among treatments, in order to remove days within each period potentially contributing

variance as a result of acclimation. All regression parameters were estimated using

regression procedures of SAS 9.2 (SAS Inst. Inc., Cary NC). Daily hay intake was

calculated by dividing weekly disappearance by 7.

Within periods, response variables (mean supplement intake, mean hay intake,

cumulative stability of supplement intake, and temporal stability of supplement intake)

were analyzed as a completely randomized design with a 7 × 2 factorial treatment

arrangement using the mixed models procedure of SAS 9.2. Limiter type, monensin

inclusion, and their interaction were included as effects in the model. Mean responses for

each limiter were compared to the control treatment using F-protected t-tests. Pairwise

comparisons among limiters were not performed. Effects were considered statistically

significant when P < 0.05. Effects are discussed as tendencies or trends when 0.05 < P <

0.15.

The effect of inclusion rate of limiters on response variables was evaluated using

regression procedures of SAS v 9.2, where inclusion rate and inclusion rate squared were

included as predictor variables in the model.

Results and discussion

Limiting agents evaluated were selected based on either potential to compliment

the nutritional profile of DDG, industry wide acceptance, or novelty. Limestone was

chosen and included at an initial rate to achieve a 2:1 calcium to phosphorous ratio for

the DDG-based supplement (NRC, 1996). Waller et al. (1980) observed increased

protein utilization when urea was included in a DDG supplement due to complimentary

30

protein attributes of urea (DIP) relative to protein composition of DDG. A combination

of limestone and urea was evaluated as an ideal complement to the composition of DDG.

Sodium chloride is easily accessible with a well-documented ability to limit intake in

self-fed applications. Calcium propionate salts may have a similar effect on palatability.

Calcium propionate is sour (acidic), provides some calcium to the mixture and may

serve as a source of additional energy in the supplement, in contrast to entirely inorganic

ingredients. Finally, malic acid was evaluated due to its intake reduction characteristics

in limited application (Foley et al., 2009) and its use in flavoring applications in the food

industry. Monensin was included in the design based on prior observations of

supplement intake reduction (Muller et al., 1986) and its effect on apparent energy value

of diets.

Baseline

Supplement intake. Mean daily supplement DM and OM intakes during the

acclimation period were 3.03 kg and 2.83 kg, respectively. There were no differences in

OMI (P = 0.56) among heifers assigned to receive different limiter treatments, nor

among heifers assigned to receive treatments with or without monensin (P = 0.92).

Additionally, no limiter × monensin combinations (P = 0.84) were detected. These

expected results confirm similarity among heifers at the initiation of the trial, and that

subsequent differences in consumption were likely not the result of individual variation.

Cumulative stability. Measures of supplement OM intake variability were not

different among treatments during the acclimation period (P = 0.93). Neither inclusion

of monensin (P = 0.81) nor combinations of assigned limiter × monensin (P = 0.91)

31

affected intake variability. Mean supplement OMI variability was 0.86 kg. As expected,

CV for OMI was not affected by limiter (P = 0.95) or monensin (P = 0.83). In the

absence of agents, no limiter × interaction was detected (P = 0.90). Results of analysis

on cumulative stability in this period indicate that differences in subsequent periods are

not due to individual response to DDG.

Temporal stability. Changes in supplement OM intake over the first four days of

collection were not different among treatment groups (P = 0.60). Numerically, OM

intake decreased daily by 0.11 kg. Neither monensin (P = 0.37) nor combination of

limiter × monensin (P = 0.60) affected temporal change.

Hay intake. Consumption of forage was not different among treatment

assignments (OMI, P = 0.56) and no differences were detected between groups receiving

treatments with or without monensin (P = 0.92). As expected, no limiter × monensin

combination was present (P = 0.84). Baseline OM intake of hay among all treatment

groups was 0.99 kg/d.

Treatment Period 1: Initial rate

Supplement intake. The degree by which voluntary consumption of a limiter-

containing feed is reduced relative to that of an unadulterated feed of the same base is

most indicative of a limiting agent’s potential. When intake limiters in this study were

included in supplement at the initial rates, OM intakes among treatment groups were

affected (P = 0.02). Relative to CONT, NACL reduced supplement OMI (P < 0.01);

MLAC (P = 0.14) and LIUR (P = 0.11) tended to reduce supplement OMI compared to

DDG alone. As a percentage of BW, this level of salt intake (0.14%) is consistent with

32

typical inclusion levels of 0.05 to 0.15% BW when used as a limiter (Kunkle et al.

2000). Addition of monensin did not influence supplement OM intake (P = 0.86), and no

limiter × monensin combination effects on supplement OM intake were observed (P =

0.66). Supplement intake means and variation measures for limiter treatments within the

initial rate period are shown in Table 5.

Based on estimates of the critical value (days) required to achieve stable intake

after introduction of the supplement, a separate analysis was conducted over the final 7 d

of the measurement period. Using this truncated data, mean supplement OMI was

diminished by NACL (P = 0.02) relative to CONT, with a similar response observed in

heifers provided MLAC (P = 0.05). No other treatments effectively reduced supplement

intake levels from those of heifers assigned CONT. Addition of monensin had minimal

effect on supplement OMI (P = 0.34) during the last 7 d of the first experimental period

and no limiter × monensin interaction was observed (OMI, P = 0.60).

Published reports of ad libitum intake levels of DDG are not available.

Consumption levels observed in this experiment were much higher than expected. Over

the final 7 d of the initial treatment period, and at an initial BW of 191 kg, heifers

provided unregulated supplement consumed 2.5 % of their BW as DDG, which is

substantially higher than provisions in previous research which typically peaked near

1.5% BW (Griffen et al., 2009). Based on these high levels of unrestricted consumption,

effective means to control intake are essential to the use of DDG as a self-fed source of

supplemental nutrients.

33

Table 5. Period 1 intake of hay and supplement, and supplement intake variance measures of a self-fed dried distillers’ grain supplement fed to growing beef heifers

Treatment1

CONT CAPR LIME LIUR MLAC NACL UREA SE L2 M3 L × M4

---------------------------------------------------------------------DMI, kg/d---------------------------------------------------------------------- 14 d Hay Intake 1.50 1.97 2.00a 1.95 2.33a 2.66a 1.56 0.18 0.01 0.16 0.51 Supplement Intake 4.27 3.86 4.01 3.65 3.57 2.64a 4.11 0.34 0.03 0.87 0.55 Cumulative stability

1.14 1.20 1.35 1.29 1.04 1.41 0.97 0.14 0.21 0.19 0.17

Temporal stability

0.15 0.22 0.23b

0.20 0.05b

0.25a

0.11 0.04 0.01 0.04 0.08 last 7 d Hay Intake 1.12 1.54 1.60 1.67

a 2.11

a 2.05

a 1.28 0.20 0.01 0.05 0.12

Supplement Intake

4.80 4.74 4.86 4.33 3.66b

3.63a

4.49 0.41 0.15 0.34 0.48 Cumulative stability 1.04 0.65a 1.20 1.17 0.97 0.69a 1.00 0.12 0.01 0.67 0.74 Temporal stability 0.26 0.12 0.31 0.28 0.22 0.19 0.15 0.07 0.45 0.63 0.92

----------------------------------------------------------------------OMI, kg/d--------------------------------------------------------------------- 14 d Hay Intake 1.39 1.80 1.84a 1.78 2.13a 2.43a 1.43 0.16 0.01 0.16 0.49 Supplement Intake 4.09 3.60 3.75 3.40 3.43 2.52a 3.94 0.31 0.02 0.86 0.66 Cumulative stability 1.06 1.10 1.24 1.18 0.96 1.19 0.90 0.12 0.35 0.17 0.13 Temporal stability 0.14 0.20 0.22b 0.19 0.05b 0.22b 0.10 0.03 0.01 0.04 0.10 last 7 d Hay Intake 1.05 1.41 1.48 1.53

a 1.93

a 1.87

a 1.18 0.18 0.01 0.05 0.11

Supplement Intake 4.61 4.42 4.55 4.03 3.55a 3.38a 4.32 0.37 0.12 0.34 0.60 Cumulative stability 0.96 0.59a 1.09 1.06 0.89 0.55a 0.92 0.11 0.01 0.75 0.76 Temporal stability

0.23 0.11

0.28 0.26 0.20 0.15

0.14 0.07 0.43 0.69 0.93

1Treatments were: control (CONT; no limiter); salt (NACL, 10%); urea (UREA, 2%); calcium carbonate (LIME, 1.68%); malic acid (MLAC; 3%), calcium propionate (CAPR, 3%), and calcium carbonate plus urea (LIUR, 1.68 + 2%) 2Limiter effect 3Monensin effect 4Limiter × monensin aWithin a row, means with a superscript differ from CONT at P < 0.05 bWithin a row, means with a superscript differ from CONT at P < 0.15

34

Effects of malic acid on total dietary DMI in this study were similar to previous

observations where included at a similar rate. Foley et al. (2009) observed a total DMI

reduction of 4% when inclusion was 2.5% relative to a control. However, concentrate

was pelleted and fed mixed with forage - both of which may have contributed to

depressed efficacy of malic acid as a limiter. Comparisons of total DMI between these

studies as opposed to supplement/concentrate alone are warranted due to the fact that, in

the referenced study, feed was mixed when offered to achieve a targeted 60:40

concentrate to forage ratio and was then separated at weigh back to quantify fractions. In

the current study, when malic acid was included at 3% supplement intake was reduced

by 2.5%; whereas including 10% NACL reduced supplement intake by 4.1% relative to

CONT. Foley et al. (2009) achieved a slightly greater reduction in total DMI likely due

to the fact that the malic acid inclusion was 2.5% of the total diet whereas our inclusion

rate was limited to DDG alone. Calculated inclusion of malic acid as a proportion of

total DMI would have been 1.90% during the last 7 d of the initial period.

Although the objective of this study is to evaluate limiting agents independently

against a control, it is notable that MLAC was more than two (2.02) times as effective as

NACL at reducing total DMI per unit of inclusion.

Cumulative stability. Supplementation response may be influenced by variability

in consumption. Therefore, discovering the extent to which intake limiters influence

variation is important. The standard deviation of daily supplement OM consumption

indicates the cumulative stability of supplement intake. Cumulative stability of

supplemental OMI was not affected by treatment (P = 0.35) nor monensin (P = 0.17)

35

when supplements contained the initial rate of limiter. A trend for a limiter × monensin

interaction on DDG OMI (P = 0.13) was observed where intake variability of CONT

was reduced (P = 0.03) from 1.34 kg/d to 0.78 kg/d when monensin was included. In

addition, a trend towards increased cumulative stability was observed with heifers fed

LIUR (P = 0.08) as variation decreased by 0.41kg/d with the inclusion of monensin

(Figure 1).

Comparisons of supplement OMI coefficient of variation (CV) are included

because intake means varied among treatments. Calculated CV for DDG was affected by

limiter (P < 0.01) during the initial treatment period; NACL was most variable (CV =

47%) and differed from CONT (P < 0.01). The lowest CV value for supplement OMI

was observed with heifers offered UREA (CV = 24%) followed by CONT (CV = 26%).

Monensin inclusion did not affect CV of supplement OMI (P = 0.40) though a tendency

for limiter × monensin combination effect was detected (P = 0.09). When monensin was

included in the supplement, OM intake CV was reduced among heifers consuming

CONT (P = 0.06) and LIUR (P < 0.01) by 54% and by 57%, respectively. In addition, a

numerical decrease in supplement OMI CV was observed when monensin was included

in combination with sodium chloride. An apparent increase in supplement OMI CV was

detected when monensin was included in MLAC and UREA.

36

Figure 1. Cumulative stability of supplement OMI by treatment during the initial rate period. An "**" denotes significance at P < 0.05. An "*" denotes significance at P < 0.15.

When intake variation associated with treatment acclimation was removed,

differences in OMI variability among treatments were magnified (P < 0.01). Heifers

provided NACL (P < 0.01) and CAPR (P < 0.01) had lower supplement OM intake

variation measures than those offered CONT. No other treatments differed from CONT

in cumulative intake stability. In summation, treatments (MLAC and NACL) that

effectively reduce DDG intake at these inclusion rates would be expected to do so

without increasing the intake variability relative to that observed in heifers offered

CONT.

During the last 7 d of the experimental period, monensin did not affect

cumulative stability of supplemental OMI (P = 0.76) and no limiter × monensin

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

Inta

ke v

aria

tion,

kg

Treatment

No Monensin Monensin

37

interaction was detected (P = 0.76). Absence of a monensin effect on variation is

contradictory of some previous findings (Burrin et al., 1988; Stock et al., 1995; Paisley

and Horn, 1996).

As a result of cumulative stability differences in the latter half of the period, it

appears that acclimation to supplement during the initial days may have masked some

influence of treatment. Regardless of monensin inclusion, measures of cumulative

stability of NACL and LIUR during the terminal portion of the period were similar to

those of during the entire period when supplement contained the ionophore. This

suggests that although no overall treatment effect exists, monensin may aid in reducing

variation in supplement intake resulting from initial exposure to sodium chloride or a

combination of limestone and urea.

Temporal stability. A supplemental regimen to deliver nutrients or increase

carrying capacity may be either short- or long-term. In either case, the ability of a self-

fed supplement to be consumed at a stable rate over length of time - withstanding

possible acclimation and/or aversion - is a valuable attribute. Supplements consumed

with greater consistency over time, i.e., exhibiting temporal stability, will require less

frequent adjustment to formulation and/or allowance to match targeted intakes. Mean

rates of change in daily supplement OMI (slope of regression of intake on days) were

used as indexes of the temporal stability of supplement intakes.

When limiters were included in supplements at the initial rates, temporal stability

of supplement OMI was affected by limiter (P < 0.01) as well as monensin (P = 0.04). In

addition, an interaction of limiter × monensin tended to influence temporal stability of

38

supplement OM consumption (P = 0.10). Supplement OMI tended to increase at a

greater rate by heifers assigned NACL (P = 0.010) and LIME (P = 0.10) relative to

CONT. In contrast, supplement OMI of MLAC tended to increase over time (P = 0.06),

but at a more modest rate than intake of OM from CONT. Increasing intake of all

treatments over time suggest that heifers became acclimated to DDG and all limiting

agents, although to different degrees.

Inclusion of monensin improved temporal stability by reducing daily OMI

change by 0.05 kg/d when included in the supplement. Interaction of limiter × monensin

resulted in more modest increases in daily supplement OM intake by heifers offered

CONT (P < 0.02) and NACL (P < 0.02) when monensin was included. Daily

consumption was reduced by 0.16 kg OM/d in both treatments. In addition, temporal

stability of supplement OMI tended to improve (P = 0.14) by 0.09 kg OM/d with the

inclusion of monensin in heifers fed LIUR. Enhancements in temporal stability of

supplement intake, generally and in combination with salt, are consistent with earlier

reports of fewer required changes to limiter inclusion when formulated to include

monensin (Muller, 1986).

Subsequent to removing data preceding the point of intake stability, analysis

indicated that neither limiter (P = 0.43) nor monensin (P = 0.69) affected temporal

stability of supplement OM intake. In addition, removal of the initial 7 d in the period

removed the tendencies for a limiter × monensin interaction (P = 0.93).

Over time, cattle may develop an aversion and reduce daily consumption

possibly due to post-ingestive feedback (Provenza, 1995), become acclimated to the

39

limiter and consume more supplement, or sustain a constant level of intake. Within this

set of observations, heifers consuming CONT, UREA, LIME, MLAC, and LIUR all

consumed more supplement during the latter portion of the initial rate period relative to

the overall mean. However, none of the limiter containing treatments differed from

CONT in their degree of daily supplemental OMI change. During the truncated portion

of the initial rate period, OMI of CONT increased by 0.23 kg/d. Therefore, from a

temporal stability standpoint, a limiter would be effective if its absolute value rate of

change was 0.23 kg/d or less. No treatments resulted in daily intake changes different

from CONT and only LIME (0.28 kg) and LIUR (0.26 kg) had daily changes in

supplement OM intake numerically greater than CONT.

Mean daily supplement OMI change by heifers not fed monensin during the

entire period was +0.18 kg/d. After days were removed to allow for acclimation, mean

DDG consumption by heifers offered monensin increased by 0.21 kg/d. This data

suggests that improved temporal stability by CONT and NACL treatment groups during

the entire period was likely a result of a palatability response to monensin and that an

acclimation occurred. From this, it appears that including monensin at the rate included

here and in combination with the other agents at their respective levels will not influence

temporal stability of supplement intake.

Hay intake. Encompassing the entire 14-d initial treatment period, hay OMI was

affected by limiter (P < 0.01) with UREA being the only treatment group to consume a

similar amount to CONT (P = 0.84). Heifers fed NACL, MLAC, and LIME (P = 0.04)

consumed more hay OM (P < 0.01) than those offered CONT, whereas heifers

40

consuming CAPR (P = 0.07) and LIUR (P = 0.08) tended to consume more. Monensin

did not influence OMI of hay (P = 0.16), though consumption was numerically

decreased by 0.17 kg/d. No limiter × monensin interaction was detected for hay OMI (P

= 0.49). MacDonald and Klopfenstein (2004) estimated that hay DMI would decrease

0.78 kg per kg of supplement consumed up to 1.91 kg/d supplement. Morris et al. (2005)

estimated forage intake by beef heifers would decrease at a more modest rate of 0.24 or

0.15 kg/d with high quality and low quality forages, respectively, when supplements

were offered at rates more comparable to those observed in our study (2.72 kg/d). When

supplement intakes from the initial treatment period were included in the linear

prediction model of Morris et al. (2005), actual hay consumption was 52% of the amount

predicted with all treatment groups having an actual to estimated ratio less than 1.

Heifers consuming CONT consumed the most supplement and least amount of hay

(34%) relative to the predicted hay DMI of 3.57. Heifers assigned NACL had the highest

actual hay consumption relative to predicted amount (60%).

Hay OMI during the last 7 days of the initial period was significantly affected by

limiter (P < 0.01). Heifers fed LIUR, NACL and MLAC consumed more hay than those

offered CONT (P < 0.05). Heifers consuming LIME (P = 0.09) and CAPR (P = 0.15)

tended to have increased hay intake. It would appear that decreases in hay intake relative

to control were result of forage substitution.

Adding monensin to the supplements resulted in a decrease in daily hay OMI by

15.81% (P < 0.05). These reductions are similar to those observed in cows on winter

range (19.6% decrease; Lemenager et al., 1978). A tendency for a limiter × monensin

41

interaction was present for daily hay OMI (P = 0.11). Inclusion of monensin in the

MLAC treatment reduced daily hay intake by 1.11 kg/d (P < 0.01), and tended to reduce

hay OMI when heifers were fed UREA (P = 0.12), but had minimal influence on hay

OMI for other treatments. Figure 2 contains measures of limiter × monensin effect on

hay OMI.

Figure 2. Hay OMI by treatment during the final 7 d of the initial rate period. An “*” denotes significance at P < 0.01.

Predicted hay intake based on the model of Morris et al. (2005) for the last 7 d of

the initial supplementation period was slightly less than for the entire period due to

increased supplement intake. Observed hay intake during the final 7 days were only a

fraction (46%) of modeled values. Supplement DM intakes of CONT, CAPR, and LIME

0.00

0.50

1.00

1.50

2.00

2.50

3.00

OM

Inta

ke, k

g/d

Treatment


42

were similar though hay intake by heifers consuming CONT was 34%lower than

predicted values, whereas hay intake by heifers consuming CAPR and LIME were 46%

and 45% of predicted values, respectively. By contrast, DDG intake was lowest by

heifers offered MLAC and NACL. Forage intake was similar among these treatment

groups with actual:estimated ratios of 0.54:1 and 0.55:1. Figure 3 shows supplement and

hay DMI during the last 7 d of the period. The consistency by which hay was consumed

in much lower amounts by all treatment groups suggests that the reduction is not related

at these rates to specific treatment feedback but, instead, likely due in some part to the

fact that supplement was consumed at a much higher rate in this study than in others

(Morris et al., 2005). Additionally, use of linear prediction models for hay intake that

were developed with lower levels of supplement intake than observed in this study may

not be appropriate for estimating forage intake in this experiment.

Due to the objective of this study, no treatment group was assigned forage alone;

thus, a precise measure of forage replacement by DDG is not available. Lower levels of

actual hay consumed relative to modeled predictions may be due to higher supplement

intakes. Supplement consumption during the final portion of the initial rate period was

1.97% BW. This level approaches a two-fold increase in the highest DDG level (kg/d)

for forage-fed cattle reported in the literature (Klopefenstein et al., 2007). Mean total

DMI (hay + supplement) across all treatments during the final 7 d of this period was

3.14% BW. Heifers fed LIME consumed the most total dietary DM per unit of BW

(3.38%) whereas those provided MLAC, NACL, and UREA consumed the least (3.02).

43

Figure 3. Supplement DMI by treatment during the final 7 d of the initial rate period. Predicted hay estimates as a result of supplement intake are derived from: y = -0.5312x + 12.864 (Morris et al., 2005).

Treatment Period 2: 2X initial rate

Supplement intake. When limiting agents were included at double the initial rate,

supplement OM intake was affected by limiter (P < 0.01, Table 6.) Daily supplement

OM consumption of NACL and MLAC was lower than CONT (P < 0.01) whereas OMI

of LIUR tended (P = 0.08) to be consumed at a reduced rate. No effects on supplement

OMI by inclusion of monensin (P = 0.47) or the interaction of limiter × monensin (P =

0.62) were detected.

As with data in the initial treatment period, the first seven days of the second

treatment period were removed and data from the final 7 d of the observation period

were analyzed in order to reduce intake variability related to supplement acclimation.

0

1

2

3

4

5

6

CONT CAPR LIME LIUR MLAC NACL UREA

DM

I, kg

/d

Treatment

Supp. Act. Hay Pred. Hay

44

During the final 7 d of the observation period, supplement OM intake was effected by

limiter (P < 0.01) as intakes of NACL and MLAC were both reduced (P < 0.01) relative

to CONT with respective means only 45% and 60% of CONT. Heifers fed LIUR

consumed supplement OM at levels that tended to be lower (P = 0.12) than CONT.

Neither monensin (P = 0.49) nor a combination of limiter × monensin (P = 0.27)

produced an effect on DDG intake. Similar supplement OM intakes of LIME (P < 0.60)

and UREA (P < 0.81) relative to CONT suggest that the tendency observed with LIUR

resulted from either a combination effect of the agents or was due to their cumulative

proportion in the supplement.

Consumption of supplement limited by salt at this level is approximate to the

2.97 kg DM/d reported by Schauer et al. (2004) when formulated inclusion was 16%.

Inclusion of malic acid as a percentage of total OMI during this period was 2.63%

45


Treatment1

CONT CAPR LIME LIUR MLAC NACL UREA SE L2 M3 L × M4

---------------------------------------------------------------------DMI kg/d---------------------------------------------------------------------- 14 d Hay Intake 1.82 2.42a 1.66 2.18 3.49a 3.90a 1.71 0.22 0.01 0.01 0.01 Supplement Intake 4.92 4.60 5.20 4.27 2.64a 2.20a 4.99 0.37 0.01 0.58 0.49 Cumulative stability

0.96 0.75 0.86 0.69

0.88 0.83 0.90 0.11 0.63 0.62 0.18

Temporal stability 0.01 0.07 -0.02 0.05 0.07

0.05

0.04 0.03 0.28 0.48 0.24 last 7 d Hay Intake 2.06 2.49 1.97 2.57 4.09

a 4.50

a 1.73 0.29 0.01 0.03 0.02

Supplement Intake

4.96 4.82 5.03 4.42 2.88a

2.39a

5.04 0.36 0.01 0.59 0.20 Cumulative stability 0.81 0.67 0.93 0.53 0.71 0.97 1.01 0.15 0.20 0.36 0.86 Temporal stability -0.06 0.12a 0.12a 0.09b 0.16a 0.16a 0.15a 0.06 0.13 0.05 0.03

----------------------------------------------------------------------OMI kg/d--------------------------------------------------------------------- 14 d Hay Intake 1.66 2.20a 1.52 1.99 3.17a 3.54a 1.56 0.19 0.01 0.01 0.01 Supplement Intake 4.69 4.21 4.64 3.89b 2.59a 2.00a 4.79 0.33 0.01 0.47 0.62 Cumulative stability 0.88 0.69 0.78 0.62a 0.82 0.58 0.83 0.10 0.22 0.51 0.15 Temporal stability 0.01 0.06 -0.02 0.04 0.07 0.04 0.04 0.03 0.30 0.47 0.23 last 7 d Hay Intake 1.88 2.26 1.79 2.34 3.71

a 4.08

a 1.58 0.26 0.01 0.03 0.02

Supplement Intake 4.72 4.41 4.49 4.02b 2.81a 2.14a 4.83 0.33 0.01 0.49 0.27 Cumulative stability 0.75 0.61 0.84 0.48 0.66 0.68 0.92 0.13 0.22 0.39 0.86 Temporal stability

-0.05 0.11

a 0.11

a 0.08

b 0.15

a 0.11

a 0.14

a 0.05 0.13 0.05 0.02

1Treatments were: control (CONT; no limiter); salt (NACL, 20%); urea (UREA, 4%); limestone (LIME, 3.36%); malic acid (MLAC; 6%), calcium propionate (CAPR, 6%), and limestone plus urea (LIUR, 3.36 + 4%) 2Limiter effect 3Monensin effect 4Limiter × monensin aWithin a row, means with a superscript differ from CONT at P < 0.05 bWithin a row, means with a superscript differ from CONT at P < 0.15

46

whereas sodium chloride comprised 6.88% of intake. This level of malic acid as a

percentage of total diet is similar to that of Foley et al. (2009) who reported a reduction

in total intake of 4%. Greater reductions of total feed intake in this study may be the

result of separate hay feeding. Hay intakes provided later depict compensation of

supplement consumption by increased forage intake. In comparison of supplement OM

intake reduction per unit of limiter inclusion, MLAC limited intake 5 percentage units

with each increment included whereas sodium chloride reduced intake roughly 2.7

percent for every unit formulated. Therefore, malic acid reduced supplement OMI

roughly 1.85 times more effectively than sodium chloride at these levels.

Cumulative stability. Variation in supplement OMI over the course of the second

treatment period was not affected by limiter (P = 0.22) nor monensin inclusion (P =

0.51). A limiter × monensin interaction tended to influence cumulative stability of

supplement OMI (P = 0.15) as variation associated with MLAC increased by 0.34 kg/d

with the addition of monensin (P = 0.07; Figure 4). Numerical differences in cumulative

stability among treatments indicated that none of the limiting agents applied at their

respective rate will improve or disrupt the cumulative stability of DDG fed alone. No

monensin effect (P = 0.85) or limiter × monensin interaction (P = 0.68) was detected.

Variation as a proportion of supplement OMI (CV) was different among limiters

(P < 0.01) where heifers fed NACL (28%) and MLAC (32%) produced a greater degree

of intake variation relative to CONT (19%, P = 0.01). No other treatments were

significantly or numerically more variable than cattle offered unadulterated DDG.

47

Figure 4. Cumulative stability of OMI by treatment during the intermediate rate period. An “*” denotes significance at P = 0.07.

Cumulative stability measures of supplement OM intake during the last 7 days of

the treatment period were not different among limiters (P = 0.22) and no monensin effect

was detected (P = 0.39). Additionally, no limiter × monensin interaction was detected (P

= 0.86). Mean cumulative stability measures of supplement OMI across treatments

decreased from the last 7 days of the initial treatment period (0.87 kg) to the last 7 days

of the second treatment period (0.71 kg). Only NACL resulted in a noticeably decreased

cumulative stability of supplement OMI (0.55 kg to 0.68 kg). All other treatments either

approached replication or reduced intake volatility which may suggest that heifers were

still adjusting to the supplement. This reasoning is not refuted by the fact measures of

temporal stability in the second half of the initial treatment period indicated that

supplement OMI was increasing for all treatments.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Inta

ke v

aria

tion,

kg/

d

Treatment


48

Coefficient of variation for supplement OMI over the final 7 d of the period was

affected by limiter (P = 0.01) and tended to be influenced by monensin (P = 0.13).

Supplement OM intake CV of NACL (31%, P < 0.01) and MLAC (27%, P < 0.04) were

greater than CONT (16%). Supplement intake variation expressed as CV of supplement

OMI was reduced numerically from 22% to 18% when monensin was included.

Combination of limiter x monensin had no affect (P = 0.39) on CV of supplement OMI.

Mean CV of supplement OMI among all treatments during the last 7 d of the second

period was 2.14 percentage points lower than the last 7 d of the initial rate period

indicating that cumulative stability was improving a faster rate than supplement intakes

declined. This value was depressed by NACL which was the only treatment not to

decrease CV of supplement OMI. Coefficient of variation of NACL OM intake

increased from 22% in the initial period to 31% in the intermediate rate period.

Temporal stability. Inclusion of limiting agents at twice the initial rate produced

no differences in temporal stability of supplement OMI due to limiter (P = 0.30) or

monensin (P = 0.47) In addition, no effect of a limiter × monensin combination was

detected (P = 0.23).

Using abridged data from the second treatment period, temporal stability of

supplement OMI tended to differ by limiter (P = 0.13) with all treatments excluding

CONT being consumed at a higher rate each day. All treatments differences from CONT

(P < 0.05) were significant with the exception of LIUR, which tended to increase (P =

0.07) consumption but at a lower rate. Inclusion of monensin in the supplement tended

to reduce (P = 0.06) temporal variation of supplement OMI from +0.13 kg/d to +0.05

49

kg/d. A limiter × monensin interaction on supplement OMI was detected (P = 0.02)

resulting in reduced consumption consistency of CONT (P = 0.02) from +0.06 kg OM/d

to -0.18 kg OM/d with the addition of monensin whereas temporal variation in heifers

offered UREA improved (P < 0.01) from +0.29 kg OM/d to 0.00 kg OM/d. Heifers

offered LIUR tended to consume supplement OM with more temporal variation when

the supplement contained monensin (P = 0.06). Figure 5 contains measures of

interaction influence on OMI temporal stability.

Results of CONT and NACL responses when combined with monensin are in

agreement with those of Muller et al. (1986) though previous literature appears to be

vacant of effects on temporal stability due to limestone, urea, or a combination with

monensin. Interactions of limiter × monensin in this period suggest that limiting agents

may not have been incorporated at high enough rates in the initial treatment period

where no response was not detected. That is to say that since rate of monensin inclusion

was not different between periods, increasing proportion of limiter was responsible for

provoking the combination effect. However, one could oppose certainty of this notion by

referencing the conflicting results on monensin effect which produced no difference in

temporal stability of supplement intake during the same time frame in the initial period

but tended to reduced temporal variation here when formulated inclusion was

unchanged. These results are difficult to explain and, although results of monensin

inclusion in this period were deemed significant via statistical analysis, the nature of

inconsistent results among treatment periods generates doubt in application to improve

50

temporal intake stability alone or in unison with any limiting agent other than sodium

chloride.

Figure 5. Temporal stability of supplement OMI by treatment during the final 7 d of the intermediate rate period. An "**" denotes significance at P < 0.05. An "*" denotes significance at P < 0.15.

Hay intake. Analysis of hay OM intakes over the course of the entire second

period produced a significant a response to limiter (P < 0.01), monensin (P < 0.01), and

limiter × monensin interaction (P < 0.01). Relative to CONT, NACL (P < 0.01), MLAC

(P < 0.01), and CAPR (P < 0.03) consumed more hay OM daily. No other treatments

differed. Inclusion of monensin decreased daily hay OMI by 0.40 kg. Heifers consuming

MLAC consumed less hay OM (P < 0.01) when the supplement contained monensin and

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

Inta

ke c

hang

e, k

g/d

Treatment


51

were the only treatment group exhibiting a significant response to a limiter × monensin

interaction though NACL tended (P = 0.07) to have the same effect.

Among treatment groups, mean hay DMI for the overall period was closer to

predicted levels of 66% using the linear model of Morris et al. (2005). Consumption of

supplement limited by sodium chloride was lowest among treatments and resulted in

most accurate hay DMI relative to prediction (86%), whereas heifers fed LIME

consumed the most supplement and consumed only 54% of expected forage

Analysis of data after removing the initial 7 d of the second treatment period

continued to detect effects by limiter (P < 0.01) and monensin (P = 0.03) on hay OMI. In

addition, an interaction of limiter × monensin also persisted (P < 0.02). Heifers assigned

supplements containing NACL and MLAC both consumed more hay OM (P < 0.01)

relative to CONT. Including monensin in the supplement decreased hay OMI by 0.45

kg/d. As a product of limiter × monensin interaction, hay OM intakes by heifers

consuming MLAC (P < 0.01) and NACL (P = 0.04) were reduced by respective

measures of 2.15 kg/d and 1.18 kg/d when monensin was included. Figure 7 depicts

OMI values relative to the interaction over the final 7 d of the period.

As with observations from the initial treatment period, supplement intakes were

generally higher in the last 7 d relative to the entire period. However, hay intakes during

the current period increased along with supplement consumption which is trend reversal

from the initial rate period. This suggests that although supplement intake increased,

limiters may have limited intake to an extent and that heifers relied on forage to reach

satiety. Forage intakes during the final 7 d of the second treatment period were 75% of

52

predicted by the Morris et al. (2005) model. Hay DMI by heifers consuming NACL was

higher than predicted (1.06:1) with all others being lower than projected (Figure 8). If

the assumption is made that lower hay intake during the initial rate period was attributed

to the level of supplement consumption, then results here - where mean supplement

intake was higher and actual hay consumption approached predicted levels - may

indicate that an increase in heifer growth and gut capacity over the 14 day span was

enough to accommodate intakes.

Figure 6. Hay OMI by treatment during the final 7 d of the intermediate rate period. An “**” denotes significance at P < 0.01. An “*” denotes significance at P = 0.04.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

OM

I, kg

/d

Treatment


53

Figure 7. DMI by treatment during the final 7 d of the intermediate rate period. Predicted hay estimates as a result of supplement intake are derived from: y = -0.5312x + 12.864 (Morris et al., 2005) Treatment Period 3: 4X initial rate

Supplement Intake. When treatments contained the highest level of limiter (4 x

initial rate), supplement OMI over the entire period differed among treatment (P < 0.01)

but was not affected by monensin (P = 0.41). Supplement OM intakes of NACL (P <

0.01), MLAC (P < 0.01), and LIUR (P = 0.02) were lower relative to CONT. A limiter ×

monensin interaction (P = 0.10) tended to reduce OM consumption of MLAC by 1.80

kg/d (P < 0.01) when monensin was included. Table 7 provides intakes and intake

variation measures for the final treatment period.

Over the final 7 d of treatment period 3, intake of supplement OM continued to

be affected by limiter (P < 0.01) and consumption of NACL, MLAC, and LIUR

0

1

2

3

4

5

6

CONT CAPR LIME LIUR MLAC NACL UREA

DM

I, kg

/d

Treatment

Supp. Act. Hay Pred. Hay

54


Treatment1

CONT CAPR LIME LIUR MLAC NACL UREA SE L2

M3

L × M4

---------------------------------------------------------------------DMI---------------------------------------------------------------------- 14 d Hay Intake 2.12 2.82

a 2.20 2.88

a 3.44

a 3.97

a 1.67 0.20 0.01 0.01 0.01

Supplement Intake 4.74 5.72b

4.98 4.01 2.69a

0.96a

5.02 0.40 0.01 0.21 0.38 Cumulative stability

0.64 1.98

a 0.59 0.65 0.73 0.34

b 0.71 0.12 0.01 0.26 0.19

Temporal stability

0.01 -0.37a

-0.01 -0.07b

-0.09a

-0.03 -0.02 0.03 0.01 0.25 0.36 last 7 d Hay Intake 2.09 2.73

a 2.48 2.91

a 3.61

a 3.93

a 1.73 0.31 0.01 0.27 0.06

Supplement Intake

4.87 4.57 5.00 3.74b

2.33a

0.86a

5.03 0.44 0.01 0.17 0.39 Cumulative stability 0.51 0.57 0.49 0.48 0.48 0.27 0.69 0.11 0.27 0.98 0.10 Temporal stability

-0.07 -0.02 -0.01 -0.02 -0.14 -0.01 -0.15 0.07 0.51 0.72 0.51

----------------------------------------------------------------------OMI--------------------------------------------------------------------- 14 d Hay Intake 1.93 2.56a 2.01 2.61a 3.13a 3.62a 1.52 0.17 0.01 0.01 0.01 Supplement Intake 4.52 5.04 4.45 3.41a 2.63a 0.77a 4.75 0.35 0.01 0.41 0.10 Cumulative stability

0.59 1.73

a 0.51 0.57 0.68 0.16

a 0.66 0.10 0.01 0.28 0.17

Temporal stability 0.01 -0.33 -0.01 -0.07 -0.09 -0.01 -0.02 0.03 0.01 0.25 0.36 last 7 d Hay Intake 1.90 2.48a 2.26 2.65a 3.28a 3.59a 1.58 0.28 0.01 0.26 0.06 Supplement Intake 4.64 4.03 4.47 3.16a 2.30a 0.73a 4.76 0.40 0.01 0.32 0.14 Cumulative stability

0.47 0.50 0.42 0.42 0.45 0.13

a 0.64 0.10 0.04 0.96 0.09

Temporal stability -0.07 -0.02 -0.01 -0.02 -0.13 -0.01 -0.14 0.06 0.48 0.66 0.54 1Treatments were: control (CONT; no limiter); salt (NACL, 40%); urea (UREA, 8%); limestone (LIME, 6.72%); malic acid (MLAC; 12%), calcium

propionate (CAPR, 12%), and limestone plus urea (LIUR, 6.72 + 8%) 2Limiter effect 3Monensin effect

4Limiter × monensin aWithin a row, means with a superscript differ from CONT at P < 0.05 bWithin a row, means with a superscript differ from CONT at P < 0.15

55

continued to be consumed at a lower rate (P < 0.01) than CONT. No significant response

to monensin was detected on supplement OMI (P = 0.32). A tendency for a limiter ×

monensin effect on supplement OMI (P = 0.14, Figure 9) persisted as consumption of

MLAC decreased (P = 0.02) by 1.84 kg OM/d and LIUR (P = 0.14) tended to increase

by 1.11 kg OM/d when monensin was incorporated in the supplement.

Further intake reductions of supplement limited by sodium chloride, malic acid, and a

combination of limestone and urea enhance confidence in their efficacy to restrict intake

of DDG. A lack of response to monensin on supplement intake during this treatment

period and throughout is surprising considering previous findings (Muller et al., 1986).

Results of a limiter × monensin interaction in this set of observations are not supported

by data in the previous treatment periods and are either by chance or a response to

respective limiting agents at specific inclusion rates.

56

Figure 8. Supplement OMI by treatment during the final 7 d of the final rate period. An “**” denotes significance at P = 0.02. An “*” denotes significance at P = 0.14.

Cumulative stability. Supplement OMI variability differed among treatments (P

< 0.01) over the duration of the final period. Cumulative stability of CAPR was reduced

(P < 0.01) relative to CONT whereas variation associated with NACL organic matter

intake decreased (P < 0.01). Monensin (P = 0.28) did not affect variation of supplement

OMI and no limiter × monensin interaction was detected (P = 0.17). Variation of OMI

expressed as CV was affected by limiter (P < 0.01). Supplements containing CAPR

(36%), MLAC (30%), and NACL (33%) had CVs higher (P < 0.01) than CONT (14%).

No monensin (P = 0.82) effect or limiter × monensin interaction was detected (P = 0.74).

Analysis of data after removal of supplement adaptation days continued to show

a treatment effect (P = 0.05) on cumulative stability of supplement OMI as variation of

0.00

1.00

2.00

3.00

4.00

5.00

6.00

OM

I, kg

/d

Treatment


57

NACL intake was reduced (P = 0.02). No other treatments differed from the level of

variation of CONT. Inclusion of monensin had no effect on cumulative stability of

supplement OMI (P = 0.96) though a tendency for a limiter × monensin interaction (P =

0.09) resulted in a decreased variation of 0.47 kg OM/d (P = 0.02) by heifers offered

UREA. In addition, adding monensin to CAPR tended to increase (P = 0.15) daily

supplement OMI variation (Figure 10). Coefficient of variation of supplement OMI was

different (P < 0.01) among limiters as both MLAC (26%) and NACL (30%) were higher

than CONT (10%, P < 0.01). Monensin had minimal influence on the CV of supplement

intake (P = 0.16) though a limiter × monensin combination effect (P < 0.01) increased

supplement OMI variation of NACL from 11% to 49% when monensin was added (P <

0.01). A tendency for a reversed response due to monensin was observed with heifers

offered UREA (P = 0.14) and LIUR (P = 0.07) as respective CV values were reduced by

10% and 13% when supplement included monensin.

58

Figure 9. Cumulative stability of supplement OMI by treatment during the final 7 d of the final treatment period. An “*” denotes significance at P = 0.02.

Temporal stability. Daily change in rate of supplement OM intake change over

the entire 14 d of treatment period 3 differed by limiter (P < 0.01) as MLAC (P = 0.02)

and CAPR (P < 0.01) consumption decreased daily relative to CONT which was the

only treatment to be consumed at an increasing rate. Daily supplement OMI of LIUR

tended to decrease (P = 0.06). No monensin affect (P = 0.25) or limiter × monensin

interaction (P = 0.36) were detected.

During the last 7 d of the period, temporal stability of daily supplement OM

intake was not affected by limiter (P = 0.48) or monensin (P = 0.66). Additionally, no

limiter × monensin interaction was present (P = 0.54). Temporal stability measures, both

over the duration of treatment period 3 and during the last 7 d alone, indicate that

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20 In

take

var

ianc

e, k

g/d

Treatment


59

supplement consumption ceased to increase. Heifers offered CONT had daily

supplement intake changes greater zero (0.01 kg) during the entire period but consumed

less supplement (-0.01 kg/d) when the last 7 days were analyzed. Therefore, a couple of

conclusions can be drawn. First, heifers no longer had intakes that were influenced by

acclimation of DDG. In fact, consumption of CONT during the last 7 d of treatment

period 3 was 0.09 kg less than consumption of CONT during the last 7 d of the previous

period. Also, declining intakes would suggest that the window of limiter of inclusion

rates of all respective limiters used here would likely accommodate accurate intake level

prediction by regression procedures.

Hay intake. During the final treatment period, OM hay consumption was affected

by limiter (P < 0.01) and monensin (P < 0.01). Forage consumption by heifers fed

NACL , MLAC , CAPR , and LIUR increased (P < 0.01) relative to CONT whereas

heifers assigned UREA tended to have decreased hay OM intake (P = 0.09) relative to

CONT. When monensin was added to DDG, hay OMI decreased 0.35 kg/d. These

reductions are similar to the decreases in forage intake during treatment period 2. Mean

supplement intake during the second treatment period was 4.12 kg and mean intakes

during this period are 4.01 kg. Therefore, monensin consumption would be essentially

equal and confirms similarities in response across rates. A limiter × monensin interaction

on hay OMI (P < 0.01) was also present in the final period where inclusion of monensin

in MLAC resulted in a reduction of 1.71 kg. Including monensin in LIUR tended also to

reduce hay OMI by 0.61 kg/d (P < 0.06). Across treatments, intakes were 74% of

predictions using linear regressions (Morris et al., 1995). Heifers offered supplement

60

limited by salt consumed the least amount of DDG and consumed the most hay, though

intake was still 1.63 kg less than predicted. Heifers receiving CAPR consumed the most

supplement and were the only treatment group to match actual (2.82 kg) and predicted

(2.80 kg) hay intakes.

Hay OM intakes during the last 7 d of the final period continued to be affected by

treatment (P < 0.01) but not monensin (P = 0.26). Consumption of CONT was lower (P

< 0.01) than both NACL and MLAC. Heifers assigned LIME had higher OM hay intakes

(P = 0.04) whereas CAPR (P = 0.07) and LIUR (P = 0.07) tended to consume more hay

relative to CONT. A slight combination effect of limiter × monensin was observed on

hay OMI (P = 0.06) as heifers offered MLAC consumed less hay (P < 0.01) when

supplement contained monensin. Intake reductions due to MLAC × monensin were 1.94

kg OM/d (Figure 11).

61

Figure 10. Temporal stability of hay OMI by treatment during the final 7 d of the final treatment period. An “*” denotes significance at P = 0.01.

Across rate analysis

In order to evaluate limiter inclusion rate as a predictor of response variables in a

DDG supplement, results within limiter treatment were regressed across periods (rates of

inclusion) and subjected to statistical analysis to determine whether limiting agents alone

or in combination with monensin projected differently than DDG alone. Comparisons

were made using CONT as an independent treatment to ensure effects on response

variables were a result of limiter and rate. In addition, data was evaluated with CONT

serving as an index value by which all other treatments were compared.

Supplement intake. Intercepts of supplement OM intake were different than zero

for all treatments (P < 0.01). When regressed across rate, results indicated that

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00

DM

I, kg

/d

Treatment


62

Table 8. Regression coefficients1 of OMI values over entire 14 d periods.

Limiter2 β0 β1 β2

CAPR 3.023* ± 0.3711 0.8621* ± 0.3892 -0.0842 ± 0.1033 CAPR + M 2.246* ± 0.4791 1.171* ± 0.5025 -0.124 ± 0.1333 CONT 2.794* ± 0.3711 1.435* ± 0.3892 -0.258* ± 0.1033 CONT + M 3.207* ± 0.4791 1.24* ± 0.5025 -0.2216 ± 0.1333 LIME 2.331* ± 0.4149 1.833* ± 0.4352 -0.3082* ± 0.1154 LIME + M 1.965* ± 0.4149 2.026* ± 0.4352 -0.3685* ± 0.1154 LIUR 2.383* ± 0.4149 1.29* ± 0.4352 -0.2759* ± 0.1154 LIUR + M 2.629* ± 0.4149 0.999* ± 0.4352 -0.1832 ± 0.1154 MLAC 3.443* ± 0.4149 -0.6529 ± 0.4352 0.052 ± 0.1154 MLAC + M 2.904* ± 0.4149 0.3256 ± 0.4352 -0.0435 ± 0.1154 NACL 3.154* ± 0.4149 -0.5937 ± 0.4352 0.0299 ± 0.1154 NACL + M 3.12* ± 0.4149 -0.9662* ± 0.4352 0.2035 ± 0.1154 UREA 2.244* ± 0.4149 1.886* ± 0.4352 -0.3343* ± 0.1154 UREA + M 3.325* ± 0.4149 1.038* ± 0.4352 -0.1498 ± 0.1154

*Coefficients differ from zero, P < 0.05 1β0 = intercept, β1 = rate, β2 = rate*rate 2Treatments were: control (CONT; no limiter); salt (NACL); urea (UREA); calcium carbonate (LIME); malic acid (MLAC), calcium propionate (CAPR), and limestone plus urea (LIUR), plus monensin ( + M)

63

supplement OMI of NACL (β1, P = 0.01; β2, P = 0.03) and MLAC (β1, P = 0.02; β2, P =

0.06) could be predicted by rate of inclusion. No other treatment had rate of rate2

coefficients that differed from zero. Table 8 contains regression parameters of OM

supplement intake over the full 14 day periods.

When initial days in each period were removed to suppress variation at least

partially due to novelty, intercepts of supplement OMI were significant for all treatments

(P < 0.01) excluding CONT+M (P = 0.03). Table 9 contains results of regression

analysis of supplement intake during terminal portions of each period. Among all

treatments, only supplement intake of NACL and MLAC could be projected by rate of

inclusion. With each bifold increase in rate of limiter, supplement was reduced by

NACL (P = 0.01) and MLAC (P = 0.02). When squared rate of limiter was incorporated

into the model, NACL (P = 0.03) and MLAC (P = 0.06) were again the only treatments

exhibiting a significant response. In each case, response to squared inclusion rate

tempered the decrease in OMI associated with inclusion rate increases. Collectively,

these figures demonstrate that the most drastic response to NACL and MLAC in a DDG

supplement would be at the initial inclusion with intake reduction becoming less severe

as supplement contained larger proportions of limiter. This is intuitive assuming that a

limiter will negatively influence intake to a point that consumption levels approach zero

and reductions associated with subsequent increases in limiter are increasingly minute.

Intake by index. Due to the confounded structure of the trial, supplement intake,

cumulative stability, and temporal stability measures were divided by the mean CONT

response of each respective variable to provide a refined indication of treatment affect

64

Table 9. Regression coefficients1 of OMI values over last 7 d of periods.

Limiter2 β0 β1 β2

CAPR 4.157* ± 0.868 -0.3241 ± 0.8629 0.0258 ± 0.1523 CAPR + M 3.088* ± 1.121 0.6294 ± 1.068 -0.1216 ± 0.1966 CONT 5.69* ± 0.868 -0.2589 ± 0.8269 0.0296 ± 0.1523 CONT + M 2.406* ± 1.121 1.859 ± 1.068 -0.2657 ± 0.1966 LIME 4.989* ± 1.121 -0.125 ± 1.068 -0.0052 ± 0.1966 LIME + M 4.454* ± 0.9705 -0.5665 ± 0.9245 0.0804 ± 0.1703 LIUR 4.277* ± 0.9705 -0.3755 ± 0.9245 -0.0017 ± 0.1703 LIUR + M 4.627* ± 0.9705 0.1643 ± 0.9245 -0.0568 ± 0.1703 MLAC 5.421* ± 1.121 -2.571* ± 1.068 0.3803 ± 0.1966 MLAC + M 4.216* ± 0.9705 -0.2303 ± 0.9245 -0.0148 ± 0.1703 NACL 6.201* ± 0.9705 -2.426* ± 0.9245 0.3836* ± 0.1703 NACL + M 5.385* ± 1.121 -0.8165 ± 1.068 0.0006 ± 0.1966 UREA 3.856* ± 0.9705 0.8103 ± 0.9245 -0.2206 ± 0.1703 UREA + M 3.232* ± 0.9705 0.8274 ± 0.9245 -0.1699 ± 0.1703

*Coefficients differ from zero, P < 0.05 1β0 = intercept, β1 = rate, β2 = rate*rate 2Treatments were: control (CONT; no limiter); salt (NACL); urea (UREA); calcium carbonate (LIME); malic acid (MLAC), calcium propionate (CAPR), and calcium carbonate plus urea (LIUR), plus monensin ( + M)

65

within each period. As with the non-indexed data, within period observations were

regressed on rate and rate2 to evaluate inclusion rate as a predictor of response variables.

As expected, OM intake intercepts resulting from regressed 14-d indexed values

were differed from zero for all treatments (P < 0.01). Among all treatments, reliable

OMI prediction equations based on rate of limiter were produced for only LIUR+M (β1,

P = 0.04; β2, P = 0.08), MLAC (β1 and β2, P < 0.01), NACL (β1, P < 0.01, β2, P = 0.02),

and NACL+M (β1, P < 0.01; β2, P = 0.08). Table 10 contains results of indexed

supplement OMI regressions over entire observation periods.

Indexed OMI regressions inclusive of only the terminal seven days in each

period again resulted in an intercept of 1.00 for CONT. Results of regressing the

abridged data indicated that only supplement intake of UREA (DM; β1, P = 0.03; β2, P =

0.04) could be predicted by rate of limiter inclusion (Table 11).

66

Table 10. Regression coefficients1 of indexed OMI values over entire 14 d periods.

Limiter β0 β1 β2

CAPR 0.9271* ± 0.0776 -01074 ± 0.0932 0.0342 ± 0.0211 CAPR + M 0.996* ± 0.1687 -0.0347 ± 0.2142 0.0245 ± 0.0497 CONT 1.000* ± 0.0938 0.000 ± 0.1192 0.000 ± 0.0278 CONT + M 1.157* ± 0.0822 -0.0894 ± 0.1044 0.0156 ± 0.0242 LIME 0.8794* ± 0.0823 0.116 ± 0.0988 -0.017 ± 0.0223 LIME + M 0.8186* ± 0.101 0.134 ± 0.1212 -0.0255 ± 0.0274 LIUR 0.8685* ± 0.1201 0.0078 ± 0.1525 -0.0119 ± 0.0354 LIUR + M 1.138* ± 0.0801 -0.2527* ± 0.0962 0.0448 ± 0.0217 MLAC 1.183* ± 0.1037 -0.503* ± 0.1316 0.0864* ± 0.0305 MLAC + M 1.038* ± 0.1505 -0.2451 ± 0.1911 0.0462 ± 0.0446 NACL 1.12* ± 0.0569 -0.4909* ± 0.0762 0.0709* ± 0.0177 NACL + M 1.099* ± 0.1052 -0.4718* ± 0.1343 0.0541 ± 0.0318 UREA 0.8212* ± 0.0864 0.1596 ± 0.1096 -0.0284 ± 0.0254 UREA + M 1.231* ± 0.1312 -0.0398 ± 0.1666 0.0032 ± 0.0386

*Coefficients differ from zero, P < 0.05 1β0 = intercept, β1 = rate, β2 = rate*rate 2Treatments were: control (CONT; no limiter); salt (NACL); urea (UREA); limestone (LIME); malic acid (MLAC), calcium propionate (CAPR), and limestone plus urea (LIUR), plus monensin ( + M)

67

Table 11. Regression coefficients1 of indexed OMI values over entire last 7 d of periods.

Limiter β0 β1 β2

CAPR 0.7656* ± 0.3216 0.1214 ± 0.3111 -0.0299 ± 0.0599 CAPR + M 0.9311 ± 0.5635 0.0718 ± 0.545 -0.0104 ± 0.1049 CONT 1.000* ± 0.2272 0.000 ± 0.2198 0.000 ± 0.0423 CONT + M 0.6004* ± 0.2032 0.3258 ± 0.1966 -0.0508 ± 0.0378 LIME 0.9818* ± 0.238 -0.008 ± 0.2302 0.0087 ± 0.0443 LIME + M 0.762* ± 0.2589 0.1429 ± 0.2504 -0.0254 ± 0.0482 LIUR 0.6102 ± 0.3668 0.2967 ± 0.3548 -0.0756 ± 0.0683 LIUR + M 0.7803* ± 0.2128 0.0485 ± 0.2058 -0.0085 ± 0.0396 MLAC 1.125* ± 0.4257 -0.5028 ± 0.4118 0.0869 ± 0.0792 MLAC + M 0.6606 ± 0.7183 0.1182 ± 0.6702 -0.0255 ± 0.1272 NACL 1.08* ± 0.2246 -0.434 ± 0.2248 0.058 ± 0.0436 NACL + M 0.6612 ± 0.3342 -0.0273 ± 0.324 -0.031 ± 0.0629 UREA 0.3269 ± 0.2251 0.5777* ± 0.2178 -0.1008* ± 0.0491 UREA + M 0.8377* ± 0.3465 0.248 ± 0.3352 -0.0475 ± 0.0645


68

Cumulative stability. Regressed measures of OM intake cumulative stability over

14 d durations indicated the presence of variation among all treatments. However, only

NACL (β1, P = 0.30; β2, P = 0.03) and CAPR (β1, P = 0.13; β2, P < 0.01) yielded

equations that contained a coefficient deviating from zero and thus could be predicted by

rate (Table 12).

Removing the initial 7 d of each period resulted in no treatment with statistically

significant parameter estimates indicating that cumulative stability could not be

estimated by rate of limiter (Table 13).

Cumulative stability by index. When cumulative stability values of the full

periods were indexed against the mean of the CONT and regressed on rate and rate

squared, β2 coefficients of CAPR (P < 0.01) and CAPR + M (P < 0.01) were

substantially greater than CONT (Table 14).

When the initial seven days of each period were removed, regressions identified

LIUR as the sole treatment with predictable measures of supplement OMI cumulative

stability as a function of limiter inclusion rate (Table 15). With each rate increase,

supplement OM intake cumulative stability would be expected to decrease (P = 0.04)

and do so at a decreasing rate (P = 0.05).

69

Table 12. Regression coefficients1 OMI cumulative stability values over entire 14 d periods.

Limiter β0 β1 β2

CAPR 1.17* ± 0.2623 -0.3729 ± 0.2426 0.1379* ± 0.047 CAPR + M 0.7427* ± 0.3386 -0.1105 ± 0.3131 0.0752 ± 0.0607 CONT 0.9471* ± 0.2623 0.0889 ± 0.2426 -0.0444 ± 0.047 CONT + M 1.142* ± 0.3386 -0.1447 ± 0.3131 0.0013 ± 0.0607 LIME 1.38* ± 0.2932 -0.3363 ± 0.2712 0.0216 ± 0.0525 LIME + M 0.9695* ± 0.2932 0.1525 ± 0.2712 -0.061 ± 0.0525 LIUR 1.04* ± 0.2932 -0.0638 ± 0.2712 -0.0089 ± 0.0525 LIUR + M 1.13* ± 0.2932 -0.234 ± 0.2712 0.0152 ± 0.0525 MLAC 1.038* ± 0.2932 -0.2606 ± 0.2712 0.0347 ± 0.0525 MLAC + M 1.034* ± 0.2932 0.0457 ± 0.2712 -0.026 ± 0.0525 NACL 0.8723* ± 0.2932 0.2846 ± 0.2712 -0.1154* ± 0.0525 NACL + M 0.7862* ± 0.2932 0.0657 ± 0.2712 -0.0563 ± 0.0525 UREA 0.6614* ± 0.2932 0.2192 ± 0.2712 -0.0453 ± 0.0525 UREA + M 0.8765* ± 0.2932 0.0199 ± 0.2712 -0.029 ± 0.0525

*Coefficients differ from zero, P < 0.05 1β0 = intercept, β1 = rate, β2 = rate*rate 2Treatments were: control (CONT; no limiter); salt (NACL); urea (UREA); calcium carbonate (LIME); malic acid (MLAC), calcium propionate (CAPR), and limestone plus urea (LIUR), plus monensin ( + M)

70

Table 13. Regression coefficients1 OMI cumulative stability values over last 7 d of periods.

Limiter β0 β1 β2

CAPR 0.677 ± 0.4859 0.0549 ± 0.4703 -0.0362 ± 0.0866 CAPR + M 0.9748 ± 0.6273 -0.3159 ± 0.6071 0.068 ± 0.118 CONT 1.277* ± 0.4859 -0.4212 ± 0.4703 0.052 ± 0.0866 CONT + M 1.761* ± 0.6273 -0.8707 ± 0.6071 0.1336 ± 0.1118 LIME 1.556* ± 0.6273 -0.4974 ± 0.6071 0.0507 ± 0.1118 LIME + M 0.994 ± 0.5432 0.0794 ± 0.5258 -0.0522 ± 0.0969 LIUR 1.598* ± 0.5432 -0.6 ± 0.5258 0.0712 ± 0.0969 LIUR + M 1.635* ± 0.5432 -0.6028 ± 0.5258 0.0751 ± 0.0969 MLAC 0.6348 ± 0.6273 -0.0279 ± 0.6071 -0.0129 ± 0.1118 MLAC + M 1.068 ± 0.5432 -0.1286 ± 0.5258 -0.0066 ± 0.0969 NACL 0.3781 ± 0.5432 0.408 ± 0.5258 -0.1038 ± 0.0969 NACL + M 0.3072 ± 0.6273 0.6073 ± 0.6071 -0.1526 ± 0.1118 UREA 0.8769 ± 0.5432 0.1253 ± 0.5258 -0.0409 ± 0.0969 UREA + M 1.253* ± 0.5432 -0.505 ± 0.5258 0.0808 ± 0.0969


71

Table 14. Regression coefficients1 of indexed OMI cumulative stability over 14 d periods.

Limiter β0 β1 β2

CAPR 0.9282* ± 0.2706 -0.43 ± 0.325 0.2523* ± 0.0734 CAPR + M 1.061* ± 0.209 -0.4681 ± 0.2653 0.202* ± 0.0615 CONT 1.000* ± 0.2153 0.000 ± 0.2735 0.000 ± 0.0637 CONT + M 1.254* ± 0.2982 -0.195 ± 0.3786 0.0299 ± 0.0878 LIME 0.9874* ± 0.098 -0.0244 ± 0.1176 -0.0155 ± 0.0266 LIME + M 0.8114* ± 0.2335 0.2546 ± 0.2804 -0.051 ± 0.0634 LIUR 1.09* ± 0.2562 -0.2425 ± 0.3252 0.0609 ± 0.0754 LIUR + M 0.9062* ± 0.1381 -0.055 ± 0.1658 0.0026 ± 0.0375 MLAC 1.214* ± 0.1925 -0.4454 ± 0.2443 0.0925 ± 0.0567 MLAC + M 1.116* ± 0.2226 -0.0145 ± 0.2828 0.0161 ± 0.066 NACL 0.924* ± 0.2548 0.0857 ± 0.3415 -0.0597 ± 0.0792 NACL + M 0.8181* ± 0.219 0.0179 ± 0.2794 -0.0431 ± 0.0662 UREA 0.6895* ± 0.2228 0.1998 ± 0.2828 -0.01 ± 0.0656 UREA + M 0.7294* ± 0.1744 0.1533 ± 0.2214 -0.0344 ± 0.0513


72

Table 15. Regression coefficients1 of indexed OMI cumulative stability over last 7 d of periods.

Limiter β0 β1 β2

CAPR 0.3119 ± 0.5701 0.3569 ± 0.5515 -0.0658 ± 0.1061 CAPR + M 0.4074 ± 0.6298 0.2374 ± 0.6092 -0.0185 ± 0.1172 CONT 1.000 ± 0.564 0.000 ± 0.5456 0.000 ± 0.105 CONT + M 1.193 ± 0.7864 -0.2119 ± 0.7607 0.025 ± 0.1464 LIME 1.244* ± 0.53 -0.1268 ± 0.5127 -0.007 ± 0.0987 LIME + M 1.066 ± 0.8254 0.102 ± 0.7984 -0.0325 ± 0.1536 LIUR 2.486* ± 0.6745 -1.556* ± 0.6524 0.29 ± 0.1256 LIUR + M 1.447* ± 0.448 -0.5811 ± 0.4333 0.0961 ± 0.0834 MLAC 0.7983 ± 0.5334 0.0722 ± 0.5159 -0.0317 ± 0.0993 MLAC + M 1.675* ± 0.6239 -0.7681 ± 0.5822 0.1539 ± 0.1105 NACL -0.1232 ± 0.6442 0.9924 ± 0.6449 -0.226 ± 0.1249 NACL + M 0.2238 ± 0.5362 0.521 ± 0.5199 -0.1291 ± 0.1008 UREA 0.3482 ± 1.34 0.6815 ± 1.296 -0.0901 ± 0.2495 UREA + M 0.4824 ± 0.7974 0.5418 ± 0.7713 -0.113 ± 0.1484


73

Temporal stability. Inclusive of entire 14 d periods, regressions of supplement

OMI temporal stability across rates resulted in no differences at the intercepts (Table

16). Rate of limiter inclusion coefficients appeared indicate effects of CONT (β1, P =

0.05; β2, P = 0.03), UREA (β1, P = 0.05; β2, P = 0.04), MLAC + M (β1, P = 0.06; β2, P =

0.03), and LIUR (β1, P = 0.10; β2, P = 0.03).

A repeat of the analysis using only the terminal 7 d of each treatment period

removed the influence on each of the treatments. Intercepts of all treatments excluding

LIUR + M (P < 0.01) were essentially zero. In addition, LIUR + M was the only

treatment to have an influence of rate (β1, P = 0.04; β2, P = 0.11) on OMI temporal

stability (Table 17).

Temporal stability by index. Change in OM supplement intake over time across

full periods regressed on rate and rate2 resulted in no intercepts that differed from zero.

Among all treatments, rate of limiter inclusion of CAPR could reliably predict temporal

stability (P = 0.01) and was the sole treatment to indicate a significant response. When

rate2 was applied as a variable, CAPR (P < 0.01), CAPR+M (P = 0.01), and UREA+M

(P = 0.03) indicated a predictable effect on temporal stability change. Table 18 contains

results of entire period regressions.

When the abridged version of the data was analyzed to evaluate trends across

rates, CONT+M was the sole treatment producing a significant intercept (P = 0.03),

response to rate (P = 0.02), and effect of rate2 (P = 0.03) on supplement OMI temporal

stability relative to CONT. Values of intercepts and coefficients are contained in Table

19.

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Table 16. Regression coefficients1 of OMI temporal stability values over 14 d periods.

Limiter β0 β1 β2

CAPR 0.1229 ± 0.1740 0.1012 ± 0.1665 -0.0557 ± 0.0313 CAPR + M -0.0322 ± 0.2246 0.2174 ± 0.215 -0.0714 ± 0.0404 CONT -0.2881* ± 0.174 0.3435* ± 0.1665 -0.0689* ± 0.0313 CONT + M 0.266 ± 0.2246 -0.2315 ± 0.215 0.0431 ± 0.0404 LIME 0.2131 ± 0.1945 -0.1015 ± 0.1862 0.0121 ± 0.035 LIME + M 0.147 ± 0.1945 -0.0392 ± 0.1862 -0.002 ± 0.035 LIUR -0.1523 ± 0.1945 0.3095 ± 0.1862 -0.0773 ± 0.035 LIUR + M 0.085 ± 0.1945 0.0119 ± 0.1862 -0.0086 ± 0.035 MLAC -0.1333 ± 0.1945 0.1712 ± 0.1862 -0.0409 ± 0.035 MLAC + M -0.2714* ± 0.1945 0.3652* ± 0.1862 -0.0795* ± 0.035 NACL -0.0931 ± 0.1945 0.2272 ± 0.1862 -0.0535 ± 0.035 NACL + M -0.1718 ± 0.1945 0.2589 ± 0.1862 -0.0554 ± 0.035 UREA -0.2842* ± 0.1945 0.3733* ± 0.1862 -0.076* ± 0.035 UREA + M 0.0359 ± 0.1945 0.0172 ± 0.1862 -0.0096 ± 0.035


75

Table 17. Regression coefficients1 of OMI temporal stability values over last 7 d of periods.

Limiter β0 β1 β2

CAPR 0.0101 ± 0.2614 0.1575 ± 0.251 -0.0376 ± 0.048 CAPR + M 0.2338 ± 0.3375 -0.0341 ± 0.324 -0.0107 ± 0.062 CONT 0.4847 ± 0.2614 -0.2894 ± 0.251 0.0373 ± 0.048 CONT + M 0.6071 ± 0.3375 -0.5783 ± 0.324 0.1027 ± 0.062 LIME -0.0301 ± 0.3375 0.0858 ± 0.324 -0.0205 ± 0.062 LIME + M 0.5613 ± 0.2923 -0.2512 ± 0.2806 0.0228 ± 0.0537 LIUR 0.3708 ± 0.2923 -0.1985 ± 0.2806 0.0299 ± 0.0537 LIUR + M 0.8848* ± 0.2923 -0.5984* ± 0.2806 0.0877 ± 0.0537 MLAC 0.1531 ± 0.3375 0.0475 ± 0.324 -0.026 ± 0.062 MLAC + M 0.3547 ± 0.2923 -0.0187 ± 0.2806 -0.0265 ± 0.0537 NACL 0.0999 ± 0.2923 0.0613 ± 0.2806 -0.0191 ± 0.0537 NACL + M 0.1985 ± 0.3375 -0.1156 ± 0.324 0.0167 ± 0.062 UREA 0.1596 ± 0.2923 0.0928 ± 0.2806 -0.0436 ± 0.0537 UREA + M 0.3964 ± 0.2923 -0.2484 ± 0.2806 0.0362 ± 0.0537


76

Table 18. Regression coefficients1 of indexed OMI temporal stability over 14 d periods.

Limiter β0 β1 β2

CAPR -50.86 ± 88.77 312.8* ± 106.6 -161.6* ± 24.09 CAPR + M -25.79 ± 112.8 207.9 ± 143.2 -110.2* ± 33.21 CONT 1.000 ± 43.09 0.000 ± 54.73 0.000 ± 12.75 CONT + M 1.976 ± 65.26 -19.87 ± 82.84 10.73 ± 19.21 LIME 1.699 ± 53.01 -9.025 ± 63.67 4.705 ± 14.39 LIME + M -3.08 ± 58.29 20.95 ± 70.01 -11.05 ± 15.82 LIUR -12.27 ± 90.15 101.2 ± 114.4 -53.57 ± 26.53 LIUR + M 0.2108 ± 48.92 -0.0056 ± 58.75 0.3123 ± 13.27 MLAC -7.723 ± 53.1 63.05 ± 67.41 -33.37 ± 15.63 MLAC + M -5.999 ± 120.3 63.01 ± 152.8 -32.35 ± 35.65 NACL -1.481 ± 31.16 16.38 ± 41.75 -8.799 ± 9.684 NACL + M -0.1647 ± 7.875 5.659 ± 10.05 -2.76 ± 2.379 UREA 0.6306 ± 21.82 -0.0033 ± 27.69 0.612 ± 6.421 UREA + M -4.188 ± 23.73 33.69 ± 30.12 -18.3* ± 6.985


77

Table 19. Regression coefficients1 of indexed OMI temporal stability over last 7 d of periods.

Limiter β0 β1 β2

CAPR -2.289 ± 4.405 3.685 ± 4.261 -0.906 ± 0.82 CAPR + M -2.125 ± 5.418 3.107 ± 5.241 -0.542 ± 1.009 CONT 1.000 ± 4.085 0.000 ± 3.952 0.000 ± 0.761 CONT + M 9.117* ± 3.267 -10.09* ± 3.16 2.13* ± 0.6082 LIME 1.059 ± 3.147 -0.1133 ± 3.045 0.0517 ± 0.5859 LIME + M -0.9616 ± 4.293 3.147 ± 4.152 -0.7712 ± 0.7991 LIUR 4.001 ± 4.258 -3.557 ± 4.118 0.7107 ± 0.7926 LIUR + M -2.386 ± 3.118 4.362 ± 3.016 -0.9468 ± 0.5805 MLAC -2.756 ± 2.083 4.069 ± 2.015 -0.7094 ± 0.3877 MLAC + M 1.399 ± 6.549 -0.9934 ± 6.111 0.507 ± 1.159 NACL -2.801 ± 2.354 4.553 ± 2.356 -0.943 ± 0.4565 NACL + M 0.7029 ± 1.594 0.1736 ± 1.545 -0.0685 ± 0.2997 UREA -4.217 ± 13.01 5.887 ± 12.59 -0.8559 ± 2.423 UREA + M 3.124 ± 4.707 -3.307 ± 4.553 0.774 ± 0.8762


78

Hay intake. When mean OM intakes of all days within periods were regressed by

treatment, intercepts of CAPR (P < 0.01), CONT+M (P = 0.03), MLAC+M (P = 0.05),

and UREA+M (P < 0.01) were different from zero (Table 20). Additionally, coefficients

associated with CAPR (β1, P < 0.01; β2, P = 0.02) indicated significance by treatment

inclusion. Organic matter hay intake was also influenced by the inclusion of UREA+M

(β1, P = 0.05; β2, P = 0.07). Influence of rate on NACL+M intake was detected (P =

0.05) though intercept only tended to differentiate from zero (P = 0.09).

When indexed, forage OM intake intercepts of CAPR+M (P < 0.01), LIME (P =

0.05), LIME+M (P = 0.04), LIUR (P < 0.01), and UREA (P = 0.05) differed from

CONT. Organic matter coefficients are contained in Table 21. Only consumption of

CAPR+M appeared to be influenced by limiter inclusion (β2, P = 0.01).

Conclusion

Intake of supplements containing MLAC and NACL were consistently lower

than CONT over the course of the trial. Cumulative stability of intake was improved

with each treatment when initial days were removed to allow for acclimation and

decreased with most treatments as limiter inclusion was elevated. After removal of initial

days, intake cumulative stability of all limiter-containing treatments were essentially

equal to that of heifers offered CONT. Rates of intake change over time were less

predictable by individual period. All treatments were consumed at an increasing rate

relative to CONT during the intermediate period but did not differ during the final

period. All limiting agents served to influence supplement intake and hay intake seemed

to increase as limiters restricted supplement consumption.

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Table 20. Regression coefficients1 of sorghum x sudangrass OMI by treatment.

Limiter β0 β1 β2

CAPR 6.37* ± 0.101 7.05* ± 0.129 -1.05* ± 0.03 CAPR + M 5.56 ± 1.54 6.87 ± 1.96 -0.941 ± 0.454 CONT 6.67 ± 1.70 3.45 ± 2.16 -0.432 ± 0.501 CONT + M 5.70* ± 0.30 2.90 ± 0.38 -0.317 ± 0.088 LIME 6.83 ± 2.52 4.88 ± 3.20 -0.836 ± 0.741 LIME + M 8.46 ± 2.83 3.83 ± 3.60 -0.647 ± 0.834 LIUR 7.14 ± 1.75 4.53 ± 2.22 -0.214 ± 0.515 LIUR + M 7.84 ± 0.88 4.05 ± 1.12 -0.463 ± 0.259 MLAC 7.05 ± 2.40 14.43 ± 3.05 -2.29 ± 0.707 MLAC + M 8.69* ± 0.711 5.31 ± 0.902 -0.871 ± 0.209 NACL 6.87 ± 1.71 14.68 ± 2.17 -2.52 ± 0.503 NACL + M 5.65 ± 0.761 13.63* ± 0.966 -2.37 ± 0.224 UREA 7.34 ± 0.806 3.52 ± 1.02 -0.714 ± 0.237 UREA + M 6.14* ± 0.214 3.54* ± 0.271 -0.569 ± 0.063

*Coefficients differ from zero, P < 0.05 1β0 = intercept, β1 = rate, β2 = rate*rate 2Treatments were: control (CONT; no limiter); salt (NACL); urea (UREA); limestone (LIME); malic acid (MLAC), calcium propionate (CAPR), and limestone plus urea (LIUR), plus monensin ( + M)

80

Table 21. Regression coefficients1 of indexed sorghum x sudangrass OMI by treatment.

Limiter β0 β1 β2

CAPR 0.981 ± 0.16 0.338 ± 0.203 -0.064 ± 0.047 CAPR + M 0.826* ± 0.004 0.397* ± 0.006 -0.068* ± 0.001 CONT 1.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 CONT + M 0.888 ± 0.171 -0.034 ± 0.217 0.009 ± 0.05 LIME 1.01* ± 0.075 0.134 ± 0.096 -0.037 ± 0.022 LIME + M 1.26* ± 0.073 -0.054 ± 0.093 -0.003 ± 0.02 LIUR 1.07* ± 0.022 0.106 ± 0.028 0.007 ± 0.006 LIUR + M 1.20 ± 0.11 -0.018 ± 0.139 0.006 ± 0.032 MLAC 1.13 ± 0.443 0.973 ± 0.562 -0.184 ± 0.13 MLAC + M 1.36 ± 0.281 0.015 ± 0.357 -0.015 ± 0.083 NACL 1.09 ± 0.367 1.01 ± 0.466 -0.203 ± 0.108 NACL + M 0.88 ± 0.244 0.989 ± 0.309 -0.2 ± 0.071 UREA 1.12* ± 0.094 -0.065 ± 0.119 -0.008 ± 0.028 UREA + M 0.947 ± 0.129 0.004 ± 0.164 -0.008 ± 0.038


81

Monensin inclusion did not affect supplement intake or cumulative stability of intake.

Influence of monensin on temporal stability seemed to vary by days observed and rate of

limiter. Rate of supplement intake change was only affected by monensin during the

latter half of the intermediate rate period. Interactions of limiter × monensin were not

detected on supplement intake or cumulative stability and influence on temporal stability

paralleled monensin influence. Monensin did, however, consistently decrease hay intake

of heifers assigned MLAC.

82

CHAPTER III

COMPARISON OF SODIUM CHLORIDE AND DL-MALIC ACID AS INTAKE

LIMITING AGENTS IN A SELF-FED DRIED DISTILLERS’ GRAIN

SUPPLEMENT


the Texas A&M University Animal Care and Use Committee (AUP 2009-239).

Research was conducted at the Texas AgriLife Research Center outside of McGregor,

TX during late winter and spring of 2011.


Sixty angus-sired, weanling steers (257 kg mean initial BW) were used to

compare the efficacy of a novel intake limiting agent relative to sodium chloride when

included at identical rates in a self-fed, monensin-containing corn distillers’ grains

(DDG) supplement. Steers were stratified by weight and randomly assigned (2 steers per

pen) to pens equipped with four Calan gates (American Calan, Inc., Northwood, NH).

Each steer was fitted with keys enabling access to two Calan gate feed bunks, one

containing chopped hay and the other containing supplement. Initially, heifers were

provided daily with 1 kg of DDG and ad libitum access to sorghum x sudangrass hay in

the adjacent bunk until acclimated to the feeding system and bunk assignments. Steers

were weighed on the first day that treatments were applied.

Treatments were randomly assigned to pen and bunk. Limiting agents were

included in treatments at 4 identical rates. Each treatment, excluding negative control,

contained 66.1mg·kg-1·suppl.-1 of monensin. Treatments were: negative control, no

83

limiter (CON); monensin (RUM); sodium chloride (NACL) included at 8%, 16%, 24%,

and 32% (8NACL, 16NACL, 24NACL, and 32NACL); and malic acid (MLAC,

Baddley Chemicals, Inc., Baton Rouge, LA) included at 8%, 16%, 24%, and 32%

(8MLAC, 16MLAC, 24MLAC, and 32MLAC). Treatments were prepared in bulk

every week by combining components in a portable rotary mixer for a duration of at

least five minutes and until visual appraisal of consistency was achieved. Treatments

were sampled from mixer immediately after manufacturing of batch and composited

within week.

All animals had continuous, ad libitum access to chopped sorghum x sudangrass

hay. Hay availability was monitored daily during supplement feeding and supplied on an

individual basis when necessary. Supplement was initially fed at predetermined amounts

that were dependent upon limiter and inclusion rate after review of previous trials.

Modifications of daily supply to both conserve feed and ensure ad libitum access were

made on an individual basis. Supplement refusals were weighed daily at 0700 and

disappearance from previous day was added. Modifications to delivery amount were

applied on an individual basis throughout the trial to ensure availability and minimize

waste. Every seventh day, accumulated refusals of both supplement and hay were

sampled and discarded then replaced with fresh feed to mimic weekly replenishment of a

bulk feeder in practice. Supplement refusal samples were composited by treatment each

week whereas hay refusal sample were retained for individual steers.

Samples of manufactured treatments, unfed hay, and refusals of both were placed in a

forced-air oven at 60ºC for 96 h to determine DM content. Samples were ground to pass

84

through a 1 mm screen of a Wiley mill (Thomas Wiley, Laboratory Mill Model 4,

Thomas Scientific Co., Philadelphia, PA) and analyzed for ash, NDF, ADF, and CP.

Organic matter was calculated from ash content of a 0.5 g sample placed into a muffle

furnace (500º C) for 8 hours. Fiber content was estimated using ANKOM 200 Fiber

Analyzer (ANKOM Technologies, Inc., Macedon, NY). Crude protein values were

derived using Dumas combustion (Rapid-N-Cube, Elementar America, Inc., Mt. Laurel,

N.J.). Nutrient composition of treatments and hay are provided in Table 22.

Within periods, response variables (mean supplement intake, mean hay intake,

cumulative stability of supplement intake, and temporal stability of supplement intake)

were analyzed as a completely randomized design with a 4 × 2 factorial treatment

arrangement using the mixed model procedure of SAS 9.2. Limiter type, percentage of

inclusion, and their interaction were included as effects in the model. Mean responses for

each limiter were compared to the control treatment using t-tests. Pairwise comparisons

among limiters were not performed. Significance of all statistical analysis was declared

where P < 0.05. Reports of trends in data are limited to results where P < 0.15.

85

Table 22. Nutrient composition of treatments1 and sorghum x sudangrass hay by week.

Nutrient, % Item DM OM NDF ADF CP Week 1

8MLAC 88.93 93.34 29.48 7.94

23.88

16MLAC 88.29 93.26 25.07 6.61 21.17

24MLAC 87.87 93.98 23.36 5.72 19.35

32MLAC 92.82 94.92 22.18 5.50 17.27 8NACL

89.75 85.60 28.18 7.58 24.03 16NACL 90.82 75.96 26.04 6.87 21.27 24NACL 91.45 70.21 23.87 6.22 18.84 32NACL 87.06 57.30 19.77 5.11 17.68 CON 89.41 92.44 32.09 8.97 26.11 RUM 89.11 92.16 31.43 8.66 25.81 Hay 91.42 90.68 58.96 33.67 10.92 Week 2 8MLAC 92.88 92.06 31.01 8.09 25.17 16MLAC 92.14 93.32 29.18 7.83 22.87

24MLAC 91.54 94.41 25.01 6.56 20.59 32MLAC 92.82 94.92 22.18 5.50 17.27 8NACL

93.10 85.32 30.71 8.15 25.59 16NACL 93.00 86.44 31.49 8.45 25.03 24NACL 93.47 72.33 26.00 6.86 20.76 32NACL 94.82 60.19 21.36 5.71 17.47 CON 89.46 92.21 30.18 9.22 27.40 RUM 93.36 92.45 31.93 9.01 25.92 Hay 90.35 90.06 56.14 29.35 10.40 Week 3 8MLAC 92.90 91.40 33.44 9.41 25.42

16MLAC 91.37 92.14 29.41 8.32 23.35 24MLAC 91.54 94.41 25.01 6.56 18.59 32MLAC 89.76 93.96 25.65 6.71 16.25 8NACL

93.45 88.11 36.84 11.78 25.09 16NACL 93.25 80.69 34.00 11.29 25.03 24NACL 93.34 73.07 29.67 9.20 20.81 32NACL 94.16 62.52 26.05 8.18 18.56 CON 89.00 92.22 31.89 8.46 26.51 RUM 92.89 92.31 38.48 12.28 26.83 Hay 92.13 89.92 57.40 30.13 10.41

continued on next page

86

Table 22. (continuted) Nutrient, %

Item DM OM NDF ADF CP Week 4 8MLAC 92.83 93.80 42.30 15.41 23.79 16MLAC 90.69 93.02 35.73 12.84 20.86 24MLAC 89.11 95.01 32.09 11.60 18.59

32MLAC 89.14 95.40 27.78 9.56 16.09 8NACL

92.80 84.52 39.85 14.86 25.18 16NACL 92.89 79.12 36.86 13.64 22.50 24NACL 93.19 73.94 35.44 13.15 20.29 32NACL 94.66 60.19 30.63 11.41 17.49 CON 92.64 92.43 33.41 9.31 25.91 RUM 92.73 94.23 46.50 17.74 26.72 Hay 92.03 90.64 58.82 30.33 10.11 Week 5 8MLAC 93.01 94.27 42.06 16.89 24.38 16MLAC 91.45 95.51 38.11 13.89 21.84

24MLAC 89.05 95.40 29.43 10.85 18.08 32MLAC 89.54 96.19 28.32 10.18 16.46 8NACL

92.62 89.03 44.71 17.42 25.18 16NACL 92.46 78.53 38.60 15.03 22.60 24NACL 93.60 66.24 32.30 11.67 19.19 32NACL 93.95 57.60 28.35 10.43 16.70 CON 92.62 94.29 29.88 8.48 27.17 RUM 93.04 94.67 47.68 17.92 26.65 Hay 91.85 90.31 57.56 29.10 10.18 Week 6 8MLAC 92.34 93.88 34.91 11.43 24.46

16MLAC 90.15 93.74 28.75 9.24 21.98 24MLAC 89.05 95.40 29.43 10.85 18.08 32MLAC 89.77 96.35 26.42 8.59 16.22 8NACL

93.11 86.54 34.12 11.65 26.08 16NACL 93.13 79.49 34.42 11.71 23.43 24NACL 94.55 68.82 27.83 9.26 20.62 32NACL 93.39 60.74 24.30 14.11 18.13 CON 92.87 94.79 31.82 9.04 26.82 RUM 89.56 93.97 46.03 16.11 27.40 Hay 91.85 90.70 59.21 29.86 9.74 1Control (CON), malic acid at 8% (8MLAC), 16% (16MLAC), 24% (24MLAC),

32% (32MLAC), sodium chloride at 8% (8NACL), 16% (16NACL), 24% (24NACL),

32% (32NACL), and monensin (RUM). All except CON contained 66.1 mg/kg monensin.

mg/mg/kkmonensin.

mg/kg of monensin.

87

The effect of increasing percentage of limiters in supplement on response

variables was evaluated using regression procedures of SAS v 9.2, where inclusion rate

and inclusion rate squared were included as predictor variables in the model.


Based on the results of the initial screening trial, limiting agents malic acid

(MLAC) and sodium chloride (NACL) were employed at identical rates to compare

efficacy in limiting supplement intake. As in the initial trial, measures included intake

level to identify agent ability to decrease consumption, cumulative stability as an

indication of the regularity of nutrient delivery within a herd at a given inclusion rate,

and temporal stability as a measure of effective duration (Table 23).

Supplement intake

Comparison of supplement intake by steers fed CON and RUM indicated that the

supplement intake was not affected by monensin (DM, P = 0.66; OM, P = 0.62). As a

result, combined means of CON and RUM are used to contrast the influence of MLAC

and NACL. Intake of supplement limited by MLAC was consistently lower compared to

supplement containing NACL at identical rates. Consumption of supplement containing

8% limiter on an as-fed basis differed (DM and OM, P < 0.01) between limiter-

containing treatments and was reduced relative to unlimited feed (4.87 kg, DM).

Relative to supplement containing no limiter, DMI was 66.5 percentage units lower

when limited by MLAC (1.66 kg, DM). Similarly, intake was only 70.7% of unlimited

supplement when NACL (3.45 kg, DM) was included. Response to malic acid at this rate

was greater than predicted based on the findings in Trial 1 where a similar inclusion rate

88

of 6% resulted in a 42 percentage point reduction in DMI. However, response to NACL

in this study was comparable to the reduction in Trial 1 a formulated inclusion of 10%

inclusion in supplement resulted in DMI of 3.63 kg. In direct comparison of limiters in

this trial alone, MLAC was 2.11 times more effective at limiting intake at this rate than

was NACL on a DM basis. This response measure is almost identical to that observed in

the initial period of the first trial (2.02). When supplement in this trial contained an

incremental rate increase of limiter, consumption was 15.8% and 31.7% of unlimited

supplement on a DM basis when agent was 16MLAC and 16NACL, respectively.

Differences in intake between limiters (DM and OM, P < 0.01) at this rate were again

twice as pronounced (2.01) on a DM basis when 16MLAC (0.77 kg) was used compared

to 16NACL (1.55 kg).

Supplement containing 24MLAC was consumed at a lower rate (P = 0.01) on a

DM basis and tended to differ (P = 0.10) from 24NACL when expressed as OMI.

Reduction in DMI measured 4.37 kg when 24MLAC (0.50 kg) was included whereas

24NACL (1.16 kg) in supplement resulted in a decrease of 3.71 kg relative to

unregulated DDG. Due to the inverse relationship of organic matter content and sodium

chloride inclusion, it is likely that decreases in OMI resulted in intake values not

statistically different among treatments though DMI continued to be more heavily

altered by use of MLAC. In comparison of treatments formulated to include 24% limiter

on an as-fed basis, MLAC reduced intake 2.34 times as much as NACL. Differences in

supplement intake on a DM basis were 0.67 kg whereas supplement OMI measured only

0.35 kg.

89

Table 23. Intake, cumulative stability, and temporal stability of supplement intake by limiter and inclusion rate.

Intake Cumulative stability Temporal stability

Rate1 MLAC NACL SE P MLAC NACL SE P MLAC NACL SE P

8% DM 1.64 3.45 0.233 0.01 1.45 1.91 0.171 0.01 -0.276 0.529 0.202 0.01 OM 1.55 3.09 0.19 0.01 1.37 1.65 0.145 0.06 -0.247 0.585 0.172 0.01 16% DM 0.77 1.55 0.242 0.01 0.62 0.94 0.178 0.08 -0.08 0.331 0.210 0.06 OM 0.70 1.41 0.197 0.01 0.60 0.73 0.150 0.42 -0.118 0.58 0.179 0.01 24% DM 0.50 1.16 0.253 0.01 0.36 0.65 0.186 0.12 0.246 0.34 0.22 0.67 OM 0.55 0.90 0.207 0.10 0.35 0.44 0.157 0.57 0.499 0.645 0.188 0.44 32% DM 0.18 0.86 0.253 0.01 0.11 0.49 0.186 0.05 0.107 0.212 0.22 0.64 OM 0.17 0.58 0.207 0.05 0.11 0.25 0.157 0.37 0.077 0.351 0.188 0.15 1Inclusion rate on an as-fed basis.

90

Finally, supplement intake at 32% limiter inclusion differed (DM, P = 0.01; OM, P =

0.05) between limiting agents used. Supplement intake was mediated to a greater degree

by 32MLAC (0.18 kg, DM) relative to 32NACL (0.85 kg, DM). At this inclusion rate,

MLAC reduced intake 4.65 times greater on a DM basis than did NACL. Due to the

extent that consumption was reduced by MLAC, differences in OMI between the two

treatments were significant despite the level of sodium chloride.

Results indicating a two-fold intake reduction when supplement is limited by

MLAC relative to NACL are supported by factorial analysis. Dry matter consumption of

8MLAC was only numerically different (P = 0.71) than that of 16NACL though

differences within treatments were significant (MLAC and NACL, P < 0.01) at these

rates. Similarly, supplement DMI by steers offered DDG formulated to included 16%

MLAC was not different (P = 0.73) than those fed supplement composed of 32% NACL.

Level of DMI at inclusion rates of 16% and 32% differed within treatment (MLAC, P =

0.02; NACL, P < 0.01).

In regards to overall intake, steers assigned CON and RUM consumed a mean

9.05 kg (DM). Across the range of limiter inclusions, steers fed supplement containing

MLAC had similar total DMI values ranging from 67.98% to 76.92% of unlimited

supplement. By contrast, steers fed supplement limited by NACL expressed a total DMI

range of 69.64% to 93.53% of supplement containing no limiter. These results suggest

that an initial, lower inclusion of MLAC may lead to a relatively substantial decrease in

total DMI with progressive increments having a diminished effect (appear quadratic). On

91

the other hand, total DMI reductions by steers consuming NACL appear to roughly align

with inclusion rate (appear linear).

Reliability of inclusion rate as a predictor of supplement intake was derived by

regressing mean intakes within treatment. Table 24 contains regression coefficients for

all dependent variables. Intakes across all percentage rates resulted in intercepts that

were different from zero (P < 0.01) on both a DM and OM basis for both treatments. In

addition, significant differences from zero at both inclusion rate (DM and OM, P < 0.01)

and inclusion rate squared (DM and OM, P < 0.01) indicate a predictable response of

both MLAC and NACL on supplement intake. Each formulated inclusion percentage of

MLAC and NACL in supplement decreased DMI by 0.37 and 0.26 kg, respectively.

Response to inclusion was reduced to a degree of 0.007 when MLAC was included and

by 0.004 kg when NACL was used.

Cumulative stability

No differences in cumulative stability were detected (DM, P = 0.26; OM, P =

0.25) among steers consuming CON and RUM. Therefore, means used in comparison to

MLAC and NACL treatments are inclusive of both.

92

Table 24. Regression coefficients1 for intake, intake variance, and time stability.

Item2 β0 SE β1 SE β2 SE

MLAC3 DMI 4.067* ± 0.2997 -0.3675* ± 0.0449 0.0074* ± 0.0013 OMI 4.337* ± 0.283 -0.3445* ± 0.0424 0.0069* ± 0.0013 DMCS 2.607* ± 0.1289 -0.1641* ± 0.0193 0.0027* ± 0.0006 OMCS 2.466* ± 0.1213 -0.1546* ± 0.0182 0.0026* ± 0.0005 DMTS 0.7439* ± 0.3035 -0.1013* ± 0.0455 0.0027* ± 0.0014 OMTS 0.6541* ± 0.2902 -0.0839 ± 0.0435 0.0023 ± 0.0013 NACL4 DMI 4.980* ± 0.3073 -0.2632* ± 0.046 0.0042* ± 0.0014 OMI 4.666* ± 0.2665 -0.2544* ± 0.0399 0.004* ± 0.0021 DMCS 2.687* ± 0.1258 -0.1331* ± 0.0188 0.002* ± 0.0006 OMCS 2.526* ± 0.0991 -0.1405* ± 0.0148 0.0022* ± 0.0005 DMTS 0.9196* ± 0.2952 -0.0495 ± 0.0442 0.0009 ± 0.0013 OMTS 0.815* ± 0.2655 -0.0152 ± 0.0397 0.0001 ± 0.0012

*P-values differ at 0.05 1β0 = intercept, β1 = percent limiter, β2 = percent*percent 2DMI = dry matter intake, OMI = organic matter intake, DMCS = dry matter cumulative stability, OMCS = organic matter cumulative stability, DMTS = dry matter temporal stability, OMTS = organic matter temporal stability 3Malic acid (MLAC; 0%, 8%, 16%, 24%, 32%). All levels formulated to include 66.1 mg/kg monensin. 4 Salt (NACL; 0%, 8%, 16%, 24%, 32%). All levels formulated to include 66.1 mg/kg monensin.

93

Cumulative stability of supplement intake was improved over unlimited

supplement (2.63 kg, DM) by both limiters at all rates of inclusion. In comparison of

limiting agents, inclusion at the lowest and highest rate resulted in significant intake

stability improvements when MLAC was used relative to NACL. Intermediate rates of

limiter in supplement here tended to induce the same result on a DM basis. Both

improvement over unregulated supplement and consistency in limiter influence oppose

the erratic findings in Trial 1. Comparison of mean intake variation between treatments

formulated to contain 8% limiter differed (DM, P < 0.01; OM, P = 0.06) resulting in

cumulative stability that was reduced by 0.46 kg/d (24%) when NACL was included as

opposed to MLAC. At formulated inclusion of 16% (P = 0.08) and 24% (P = 0.12),

MLAC was more effective at stabilizing DMI by measures of 0.32 kg and 0.29 kg,

respectively. Cumulative stability of supplement intake by steers consuming 32MLAC

and 32NACL differed (P = 0.05) on a DM basis but was similar (P = 0.37) on an OM

basis. When limiting agent composed 32% of supplement, DMI variation within

treatment was decreased 0.38 kg/d (78%) with use of MLAC relative to NACL.

Analysis of cumulative stability regression values indicate that percentage and

squared percentage rate of limiter inclusion are of use in predicting cumulative stability

of both MLAC and NACL in a DDG supplement. A similar decline in cumulative

variance is predicted for both limiters (DM and OM, P < 0.01) when included at like

rates. By percentage of inclusion, MLAC tempered cumulative variance of supplement

DMI by 0.16 kg whereas NACL improved stability by 0.13 kg. Additionally,

significance of the β2 coefficient (DM and OM, P < 0.01) with both limiters suggests

94

that response to inclusion percentage will dissipate at increased levels. Improvements in

supplement DMI cumulative stability were dissipated by 0.002 kg with each incremental

inclusion of both agents. A visual reference to cumulative stability by rate in this study is

provided in Figure 11.

Figure 11. Regressed DMI cumulative stability by percentage of limiter inclusion.

Temporal stability

As with intake and cumulative stability, monensin had no affect on temporal

stability. As a collective mean, daily intake change of both CON and RUM over the

course of the trial was +0.95 kg/d.

Daily changes in supplement consumption were significantly different between

limiter-containing treatments when included at 8% (DM and OM, P < 0.01) and 16%

(DM, P = 0.06; OM, P = 0.05). At 8% inclusion, DMI decreased 0.28 kg/d when limited

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 8 16 24 32

kg

MLAC

NACL

Percentage

95

by MLAC and increased 0.53 kg/d when NACL was included. An intake reduction by

steers consuming this level of MLAC contradicts the slight temporal increase (0.16 kg)

observed in Trial 1 when supplement contained 6%. Heifers consuming DDG containing

10% salt during Trial 1 increased their daily intake to a lesser degree (0.16 kg vs. 0.53

kg) relative to steers in this trial consuming 8NACL. Organic matter intake of

supplement formulated to include 8% limiter decreased 0.25 kg/d and increased 0.59

kg/d when containing MLAC and NACL, respectively. When 16MLAC and 16NACL

were provided, DM temporal stability measures were -0.08 kg and 0.33 kg, respectively.

Organic matter of supplement including 16% limiter was consumed at a decreasing rate

(-0.11 kg/d) when limiter was MLAC and at an increasing rate (0.58 kg/d) when

tempered by NACL. Differences in temporal stability at inclusion levels of 24% (DM, P

= 0.67; OM, P = 0.44) and 32% (DM, P = 0.64; OM, P = 0.15) were undetected.

When daily mean temporal stability measures within treatment were regressed,

analysis indicated that only temporal intake change of MLAC could be reliably predicted

by inclusion rate. Intercept (0.74 kg, DM) of supplement temporal stability associated

with MLAC (DM, P = 0.02; OM, P = 0.03) as well as coefficients of percentage (-0.37

kg, DM, P = 0.03; OM, P = 0.06) and percentage squared (0.01 kg, DM, P = 0.05; OM,

P = 0.09) suggest that increasing concentration will decrease temporal variance at a

decreasing rate with progressive inclusions. On the other hand, regression of NACL

temporal shifts resulted in an intercept that differed significantly from zero (0.92 kg, DM

and OM, P = 0.01) but neither a response to percentage (-0.05, DM, P = 0.27; OM, P =

0.71) nor percentage squared (0.00 kg, DM, P = 0.51; OM, P = 0.94) proved to be useful

96

in temporal predictability. Figure 14 contains a visual comparison of regressed temporal

stability.

Figure 12. Regressed DMI temporal stability by percentage of limiter inclusion.

Hay intake. Overall, hay intake was unaffected by monensin (DM, P = 0.56; OM,

P = 0.53) or limiter type (DM, P = 0.30; OM, P = 0.29). Hay intakes by percentage of

limiter inclusion are provided in Table 25.

Table 25. Mean daily hay intakes (kg) by percentage of limiter inclusion.

MLAC NACL Percentage DM OM DM OM

0% 4.18 3.80 4.18 3.80

8% 5.33

4.88 5.02 4.57

16% 5.40 5.04 5.71 5.25

24% 5.67 5.21 5.49 5.01

32% 5.97 5.47 5.45 4.99

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 8 16 24 32

kg/d

MLAC

NACL

Percentage

97

When regressed across percentage rates of limiter inclusion (Table 26), hay

intake intercepts of both limiters differed from zero on both a DM and OM basis (P <

0.01). Percentage of limiter in supplement affected hay intake of steers fed both MLAC

(DM and OM, P < 0.01) and NACL (DM and OM, P < 0.01). With each percentage

increase of limiting agent incorporated into DDG, hay intake increased by 0.12 kg when

limited by MLAC and 0.13 kg when NACL was used. Squaring the percentage of limiter

in supplement resulted in only a slight response with both agents. Response to MLAC in

terms of hay DMI was relatively stable (-0.002 kg, P = 0.07) across the range of limiter

inclusion though the effect on hay DMI by steers fed NACL was more pronounced (-

0.003 kg, P = 0.03).

Figure 13. Regressed DMI of sorghum x sudangrass hay by percentage of limiter inclusion.

0

1

2

3

4

5

6

7

0 8 16 24 32

kg/d

Percentage

MLAC

SALT

98

Table 26. Regression coefficients1 of indexed DM and OM intakes.

Item2 β0 SE β1 SE β2 SE

MLAC3 DMI 4.296* ± 0.2657 0.1207* ± 0.0398 -0.0022 ± 0.0012 OMI 3.9145* ± 0.2466 0.1134* ± 0.037 -0.0021 ± 0.0011 NACL4 DMI 4.1812* ± 0.2730 0.1291* ± 0.0408 -0.0029* ± 0.0012 OMI 3.8038* ± 0.2567 0.1203* ± 0.0384 -0.0027* ± 0.0012

*P-values < 0.05 1β0 = intercept, β1 = percent limiter, β2 = percent*percent 2DMI = dry matter intake, OMI = organic matter intake, DM SD = dry matter standard deviation, OM SD = organic matter standard deviation, DM Slope = daily change in DMI, OM Slope = daily change in OMI 3Malic acid (MLAC; 0%, 8%, 16%, 24%, 32%). All levels included 66 mg/kg monensin. 4 Salt (NACL; 0%, 8%, 16%, 24%, 32%). All levels included 66 mg/kg monensin.

Conclusion

Intake of MLAC was consistently lower than NACL at each level of inclusion.

Cumulative stability of MLAC was improved relative to that of NACL at 8% inclusion

but differences diminished as inclusion was increased. Daily intake reductions were

more pronounced with MLAC up to 16% inclusion. Hay intake was reduced relative to

RUM by limiter inclusion up to 8% MLAC and 16% NACL.

99

CHAPTER IV

EVALUATION OF STACKED PRODUCTION TECHNOLOGIES ON ADG

OF CALVES GRAZING SMALL GRAIN WINTER PASTURES


the Texas A&M University Animal Care and Use Committee (AUP 229-239). Research

was conducted from January through April 2011 at the Beef Research Unit at Texas

A&M University, College Station, TX.


One hundred crossbred steers (240 kg mean initial BW) were used in a split-plot

design to evaluate the influence of beef production technologies on ADG over the course

of a 98-d grazing period on yearling cattle grazing irrigated winter oats (Avena sativa L.)

pastures. Steers were weighed and at weaning and received a multivalent killed viral

vaccine (Vira Shield 6+VL5, Novartis Animal Health US, Inc., Greensboro, NC) and

clostridial vaccinine (Clostri Shield 7, Novartis Animal Health US, Greensboro, NC).

Body weights were obtained again 23 days prior to the study to obtain sorting weights.

All steers originated from a single location (Texas AgriLife Research Center, McGregor,

TX) and were relocated to study site and fed hay in a drylot until prior to trial initiation.

Sub plot treatments were randomly assigned to experimental units (steers).

Whole plot treatments were hand-fed energy supplement (Table 27) fed at a rate of 0.91

kg·hd-1·d-1 with (RUM; 135 mg·hd-1·d-1) or without (CON) monensin (Rumensin 90;

Elanco Division, Eli Lilly and Co., Indianapolis, IN). Sub plot treatments were arranged

in a 2 x 2 factorial and consisted of administration of a metaphylactic (MM; Micotil 300,

100

Elanco Division, Eli Lilly and Co., Indianapolis, IN) dosed at 1.5 ml/cwt of initial BW

or no metaphylaxis (PT) and a single dose implant (I; TEG with Tylan, Elanco Division,

Eli Lilly and Co., Indianapolis, IN) given at initial day of study in the middle third of the

right ear or no implant (0). Four whole plot experimental units (paddocks) consisted of

four replicates containing equal numbers (n=3) of each sub plot treatment experimental

units whereas remaining paddocks contained on additional, randomly assigned sub plot

experimental unit. Thus, four paddocks contained 12 steers and four paddocks contained

13 steers. Paddocks were approximately 6.22 ha equating to stocking rates of 1.93 hd per

ha. Sort weights were used to allocate steers to whole plot replicates. Figure 48 depicts

layout of paddocks and treatment assignments.

Shrunk body weights were collected in the morning of d 28, 56, 84, and 105. On

the preceding days, steers were gathered in the afternoon and held overnight without

access to feed or water. Manual palpation of ear was performed to confirm presence of

implant. After weighing, steers were immediately resorted into returned to assigned

paddocks.

101

Table 27. Composition of hand-fed energy supplement fed to steers grazing oat pastures (% as-fed)

Treatment

monensin

control

Item batch 11 batch 22 batch 11 batch 22

Dried distillers’ grains 97.35% 94.51% 97.50% 94.70% Commercial mineral 2.50% 2.43% 2.50% 2.43% Molasses - 2.91% - 2.87% Rumensin 903,4 0.150% 0.146% - - 1Batch 1 was fed d 1 through 34 2Batch 2 was fed d 35 through 105 3135 and 131 mg·hd-1·d-1 of active ingredient in Batch 1 and 2, respectively 4Elanco Division, Eli Lilly and Co., Indianapolis, IN

102

Supplement was provided daily in metal troughs (3.05 meters) placed in relative

proximity to water. Every seventh day, remaining supplement was gathered prior to feed

delivery and weighed in order to calculate supplement intake·hd-1·d-1. Due to low intakes

of monensin-containing supplement, molasses (3%) was added to both diets and fed

beginning d 35. In order tom minimize effects of supplement intake variation between

dietary treatments, supplement allowance was reduced to 0.45 kg·hd-1·d-1 beginning on d

42. A timeline is presented in figure #. Samples from each batch of formulated

supplement were collected weekly. Samples were dried in a forced air oven (60º C) for

96 h for DM determination. Samples were ground to pass through a 1 mm screen of a

Wiley mill (Thomas Wiley, Laboratory Mill Model 4, Thomas Scientific Co.,

Philadelphia, PA) and analyzed for ash, NDF, ADF, and CP. Organic matter was

calculated from ash content of a 0.5 g sample placed in an ashing oven (500º C) for 8 h.

Fiber content was estimated using an ANKOM 200 Fiber Analyzer (ANKOM

Technologies, Inc., Macedon, NY). Crude protein values were derived using Dumas

combustion (Rapid-N-Cube, Elementar America, Inc., Mt. Laurel, N.J.).

Procurement of forage samples to estimate availability and nutrient content

coincided with weigh dates. Within each paddock, 8 samples of forage clipped to

approximately 2.5 cm were obtained by tossing at random a 0.1 sq meter quadrant. Each

sample was placed into a pre-weighed paper bag and dried in a forced air oven (60º C)

for 96 h to determine mean DM content. Mean sample weights were multiplied by

94512.38 to convert m2 to forage mass per ha. With each collection, samples were

composited by paddock and ground to pass through a 1 mm screen of a Wiley mill

103

(Thomas Wiley, Laboratory Mill Model 4, Thomas Scientific Co., Philadelphia, PA) and

analyzed for ash, NDF, ADF, and CP. Organic matter was calculated from ash content of

a 0.5 g sample placed in an ashing oven (500º C) for 8 h. Fiber content was estimated

using an ANKOM 200 Fiber Analyzer (ANKOM Technologies, Inc., Macedon, NY).

Crude protein values were derived using Dumas combustion (Rapid-N-Cube, Elementar

America, Inc., Mt. Laurel, N.J.).

Calves were monitored once daily for health status using a 5-point clinical illness

score. Morbidity signs including depression, ocular and nasal discharges, and respiratory

issues were pulled for temperature reading. A rectal temperature ≥ 40º C warranted

treatment by antibiotic according to label instructions and visually severe symptoms

resulted in treatment regardless of temperature. Description of clinical illness score

criteria is provided in Table 28. Steers exhibiting morbidity were treated initially with

entrofloxacin (Baytril 100, Bayer Corporation, Shawnee, MI) at a rate of 10 mg/kg BW.

Steers requiring a follow up treatment were administered tulathromycin (Draxxin, Pfizer

Animal Health, Madison, NJ). Bloat was quantified with a 4-point scoring system which

followed Paisley and Horn (1998). Values were: 0 = normal, 1 = slight distention, 2 =

distention with rumen elevated toward backline, and 3 = severe distention with rumen at

or above back level.

104

Table 28. Descriptive criteria for subjective health evaluation

Score Description

0 Normal. No clinical sign of illness.

1 Mildly abnormal respiration. Dyspnea with minor depression, gauntness, nasal and/or ocular discharges.

2 Moderatley abnormal respiration. Dyspnea with noticeable depression gauntness, nasal and/or ocular discharges.

3 Severely abnormal respiration. Pronounced dyspnea, depression, gauntness, nasal and/or ocular discharges.

4 Moribound – immobile.

Weight and ADG were analyzed using the mixed model (PROC MIXED)

procedure in SAS (SAS Inst. Inc., Cary, NC). Monensin, metaphylaxis, and implant

served as fixed effects with paddock replicate as a random effect. Forage availability and

nutrient content were analyzed using repeated measures with compound symmetry as the

covariance structure.

Supplement intake was used in the 1996 NRC model to estimate forage intake.

Body weights used in the model were means of d 0 and d 98 for each dietary treatment

group. Measures of cumulative ADG for diet × implant were used with mean intakes of

both diets to calculate differences in energy associated with dietary treatment by

adjusting forage intake to meet ADG. Difference in estimated NEg by removal of

supplement intake was attributed to supplement.

105


Initial weight

A by-treatment summary of initial BW, final BW, cumulative ADG, and ADG

within each period is provided in Table 29. Initial BW (d 0) was not affected by dietary

treatment (P < 0.28) or either of the subplot treatments (implant, P < 0.68; metaphylaxis,

P < 0.38). Additionally, no interactions were significant with measures of initial BW

(diet × implant, P < 0.25; diet × metaphylaxis, P < 0.98; implant × metaphylaxis, P <

0.86; diet × implant × metaphylaxis, P < 0.61). Interactions are summarized in Table 30.

ADG within period

Weight gain during the first 28 d period was influenced by both implant (P <

0.02) and metaphylaxis (P < 0.05). Daily gains were increased by 20.46% in steers

receiving implant and 16.41% in steers given metaphylactic treatment. No difference

was attributed to dietary treatment or any treatment interactions.

From d 29 through 56, implant use was effective (P < 0.01) in raising ADG.

Metaphylactic application did not significantly increase gains (P < 0.71) though a slight

interaction was observed between dietary treatment and metaphylaxis (P < 0.08). Diet

alone did not influence gains nor were did any other interactions.

Gains during d 57 through 84 were higher in implanted cattle (P < 0.01) and an

interaction between diet and implant was also detected (P < 0.01). Diet alone tended to

influence gains (P < 0.11) with cattle receiving RUM having 9.33% higher gains.

Metaphylaxis and other interactions did not significantly affect ADG.

106

Table 29. Mean BW and ADG by treatment of steers grazing winter oats

Diet Implant Metaphylaxis

Item1 CON2 RUM3 SEM P-value 04 I5 SEM P-value PT6 MM7 SEM P-value

BW0 233.96 245.50 6.81 .28 240.67 238.80 5.31 .68 237.78 241.69 5.31 .38 BW98 373.00 378.10 6.69 .61 368.64 382.46 5.68 .03 372.00 379.09 5.68 .26 ADG28 0.98 0.91 0.08 .55 0.86 1.04 0.07 .02 0.88 1.02 0.07 .05 ADG56 1.49 1.44 0.10 .72 1.39 1.54 0.08 .01 1.48 1.45 0.08 .71 ADG84 1.36 1.49 0.05 .11 1.33 1.52 0.04 .01 1.39 1.45 0.04 .32 ADG98 1.60 1.20 0.07 .01 1.32 1.48 0.06 .03 1.41 1.57 0.09 .74 CUM56 1.24 1.17 0.03 .22 1.12 1.29 0.03 .01 1.18 1.24 0.03 .19 CUM84 1.28 1.28 0.03 .99 1.19 1.37 0.03 .01 1.25 1.31 0.03 .09 CUM98 1.34 1.26 0.03 .13 1.22 1.38 0.03 .01 1.28 1.32 0.03 .15 1BW0 = initial BW, BW98 = final BW, ADG28 = ADG d 1-28, ADG56 = ADG d 29-56, ADG84 = ADG d 57-84, ADG98 = ADG d 85-98, CUM56 = ADG d 1-56, CUM84 = ADG d 1-84, CUM98 = ADG d 1-98 2,3CON = Control, RUM = Rumensin containing (135 mg·hd-1·d-1) 4,5PT = pull and treat (no metaphylaxis), MM = metaphylaxis (Micotil 300, 1.5 ml/100 kg BW) 6,70 = no implant, I = single dose implant (TEG + Tylan)

107

Table 30. Mean BW and ADG by treatment interactions of steers grazing winter oats (kg)

Diet1

CON

RUM

PT2 MM3 PT MM

Item6 04 I5 0 I 0 I 0 I SEM P, D*M*I7

BW0 231.83 232.09 232.77 239.17 246.38 240.81 251.71 243.13 8.82 .68 BW98 359.12 379.81 368.39 384.68 369.75 379.33 377.29 386.01 10.25 .89 ADG28 0.71 1.03 1.12 1.09 0.77 1.00 0.85 1.03 0.12 .32 ADG56 1.60 1.51 1.31 1.54 1.29 1.50 1.35 1.61 0.12 .28 ADG84 1.10 1.51 1.26 1.57 1.52 1.45 1.43 1.54 0.09 .20 ADG98 1.50 1.63 1.54 1.74 1.11 1.33 1.15 1.23 0.11 .43 CUM56 1.15 1.27 1.21 1.32 1.03 1.25 1.10 1.32 0.07 .94 CUM84 1.13 1.35 1.23 1.40 1.19 1.31 1.21 1.39 0.05 .46 CUM98 1.21 1.41 1.29 1.44 1.18 1.32 1.20 1.36 0.05 .62 1CON = Control, RUM = Rumensin containing (149 mg/kg d 1-35, 144 mg/kg d 36-105) 2,3PT = pull and treat (no metaphylaxis), MM = metaphylaxis (Micotil 300, 1.5 ml/100 kg BW) 4,50 = no implant, I = single dose implant (TEG + Tylan) 6BW0 = initial BW, BW98 = final BW, ADG28 = ADG d 1-28, ADG56 = ADG d 29-56, ADG84 = ADG d 57-84, ADG98 = ADG d 85-98, CUM56 = ADG d 1-56, CUM84 = ADG d 1-84, CUM98 = ADG d 1-98 7D*M*I = Diet × metaphylaxis × implant

108

Day 85 to 98 ADG were influenced by diet (P < 0.01) and implant (P < 0.03).

Steers consuming CON gained 33.28% more than steers fed monensin whereas

implanted steers had higher gains by 49.14%.

Cumulative ADG by period

Through d 56, significant differences in ADG were again attributed to use of

implant (P < 0.01) where steers receiving treatment had gains 14.65% higher than those

not receiving implant. Influence of metaphylaxis was not detected (P < 0.19) though

treated steers gained 5.28% more weight. Again, no differences in ADG in the period

were attributed to dietary treatment or treatment interactions.

At d 84, cumulative rate of gain was again improved by implant (P < 0.01).

Steers receiving the treatment gained 1.365 kg/d as opposed to 1.192 kg/d. Metaphylaxis

tended to increase ADG (P < 0.09) by increasing gains 4.88%. No differences were

observed as a result of supplement or interactions of treatments.

Encompassing the entire trial, use of implants improved ADG by 13.46% (P <

0.01). Gains were slightly affected (P < 0.13) by dietary treatment as steers assigned

CON supplement gained 28.08% more weight. Metaphylactic usage also increased gains

(P < 0.15; 16.65%). No treatment interactions were detected. Gains of cattle receiving

metaphylactic were 16% higher during the first 28 days on pasture and tended to be

slightly higher during days 0 to 84 and 0 to 98. Initial gain differences are nearly

identical to those provided in a summary by Wileman et al., 2009. Galyean et al. (1995)

observed no difference in ADG among steers treated with tilmicosin or a control in an

initial 56 day feeding period; however, a significant reduction in cattle pulled for bovine

109

respiratory disease was achieved. Herd health in our study was excellent and void of any

necessary treatment associated with internal abnormalities. Part of this stability may be

attributed to common origin of the cattle. Influence on ADG during the later periods are

somewhat unexpected in that most problems associated with bovine respiratory disease

and associated performance reductions are manifested within the first 45 of arrival

(Edwards, 1996). However, reviewed temporal patterns of outbreaks in feedlots suggest

that occurrence may be delayed (Babcock et al., 2009). Despite occasional late

occurrences, treatment is most effective as it relates to ADG when provided on arrival as

opposed to delay (Kreikemeier et al., 1996).

Implanting steers provided the most consistent impact among treatments in this

trial. Final body weight as well as all ADG measures both within period and cumulative

were significantly increased as a result of implantation. Mean increases in ADG among

all measures in this study were 0.17 kg/d. These results are substantially higher than

approximate reported ranges of cattle on small grains (0.08 kg/d, McCollum, 2006).

Gains relative to control from this study were identical to steers fed a distillers’ grain

supplement in a split-plot design (mean = 0.17 kg/d, McMurphy et al., 2009) evaluating

implant type though gain response in regards to implant assignment was undefined.

Interactions in this study were largely insignificant as expected due to unrelated modes

of action among between treatments.

Supplement intake

Mean DMI of dietary treatments were different overall (P < 0.01) with steers

assigned RUM consuming less than CON (0.26 vs. 0.56 kg·hd-1·d-1, respectively).

110

Within dietary treatments, supplement DMI was not different among paddocks (RUM, P

= 0.28; CON, P = 0.91). Overall, supplement containing monensin in this study was

consumed at a considerably reduced rate relative to a control. Intakes were reduced 54%

by an inclusion rate similar to that of Paisley and Horn (1996) who observed intake

reductions of 43%. As an expected result of reduced means, coefficient of variation for

weekly supplement intake was much higher in this study for supplement containing

monensin compared to a control diet. Though intakes of a monensin-containing

supplement were slightly higher, calculated coefficient of variation was much lower in

the data published by Paisley and Horn (1996) and much closer to control diet variation

measures.

Final weight

Ending BW (d 98) was significantly influenced by use of implant (P < 0.03).

Body weights were increased by a mean of 13.82 kg relative to non-implanted steers.

Neither diet (P < 0.61) nor metaphylaxis (P < 0.26) impacted final weights and no

interactions were detected.

Response to supplement

Estimation of forage intake to meet observed gains using the 1996 NRC model

indicated that supplement containing monensin resulted in an 8.45% increase in NEg

yield (CON = 1.42 Mcal/kg, RUM = 1.54 Mcal/kg). Estimated forage intake to meet

actual gain in the absence of supplement was lowest for RUM -0 (4.43 kg/d) group and

highest for CON-I (5.10 kg/d). Intake was the same for CON-0 and RUM-I (4.75 kg/d).

Neither initial nor final BW in this study was significantly influenced by dietary

111

treatment. This suggests that steers assigned monensin either compensated by consuming

more forage or were provided sufficient energy despite intake level to facilitate gains

similar to other steers consuming twice as much. Average daily gains were only

significantly influenced by diet from day 84 to day 98; however, cumulative ADG

tended to higher in steers not consuming monensin. Typically, monensin would be

expected to increase ADG (Horn et al., 1981). Therefore, atypical results of this study

are attributed to low level of supplement intake. Supplemental energy will increase ADG

on small grains pastures due to increased microbial growth and protein synthesis

(McCollum and Horn, 1990; Horn et al., 1995). Therefore, reduced intake associated

with monensin inclusion would be expected to reduce ADG response relative to steers

consuming a higher level of supplement.

Standing crop

Over the course of the trial, forage availability was unaffected by dietary

treatment (P = 0.52) and no dietary treatment × day interaction occurred (P = 0.26).

Standing crop decreased from d 0 to 56 then increased through d 98 where forage mass

peaked (6324 ± 366 kg DM/ha) resulting in a day effect (P < 0.01, Figure 16).

112

Figure 14. Standing forage (kg DM/ha) in paddocks expressed as means within collection date.

Forage mass per kg BW

Available forage per kg BW was unaffected by diet (P = 0.38) and no interaction

of diet × collection day was observed (P > 0.50). Forage allowance per kg BW was

highest at beginning to trial in paddocks where RUM was fed whereas forage availability

increased between d 0 and 56 in paddocks assigned to CON supplement. Figure 17

depicts trend in forage availability per kg BW for both diets.

4880.51 5151.2 4357.74 5898.14 6324.48

0 1000 2000 3000 4000 5000 6000 7000 8000

0 28 56 84 98

kg/h

a

Day

ab b a c c

Standing forage availibility by day (kg DM/ha)

113

Figure 15. Standing forage mass relative to mean BW of steers by dietary treatment.

When forage availability is expressed on a DM basis per 100 kg of BW, diet

tended to influence herbage mass (P < 0.18) whereas day (P < 0.01) and diet × day (P <

0.02) both had a significant impact on availability. Again, trend in forage mass

availability from d 0 and d 28 was antithetical between dietary treatments. Figure 18

provides measures at each date. Density was sufficient to support maximum gain

throughout the trial. Collectively, Pinchak et al. (1996) and Redmon et al. (1995) stated

that ranges of herbage allowance to fully support ADG potential be maintained between

20.0 and 27.3 kg DM/100 kg BW. At a minimum, forage density in this trial was

calculated to exceed 160.0 kg DM/100 kg BW.

4

5

6

7

8

9

10

11

12

0 28 56 84 98

kg fo

rage

/kg

BW

Forage availibility by day (kg/kg BW)

CON

RUM

Day

114

Figure 16. Available forage by diet and day expressed in kg DM/100 kg BW

Nutrient composition

A visual reference to nutrient trend is provided in figure 19. Nutrient content of

paddocks are expressed as means within each collection date due an absence of diet

effect or diet × day interaction for all measures (Table 31).

0 28 56 84 98 CON 166.9 556.59 163.77 269.52 437.47 RUM 191.91 277.53 190.41 279.12 431.77

0

100

200

300

400

500

600

700

kg D

M/1

00 k

g B

W

Forage availability by day (kg DM/100 kg BW)

115

Figure 17. Nutritive values of paddock forage expressed as means within collection date.

Dry matter, OM, NDF, ADF, and CP were all affected by day (P < 0.01). Crude

protein decreased from 22.7% to 8.4% over the course of the trial and was unaffected by

diet (P = 0.99) or day × diet (P = 0.79). Proportion of fiber components increased during

the study with no diet effect (P = 0.26 NDF, P = 0.28 ADF) or diet × day interaction (P =

0.40 NDF, P = 0.63 ADF).

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

100.0

0 28 56 84 98

Perc

enta

ge

Nutritive composition by day of winter oats pastures

DM OM NDF ADF CP

Day

116

Table 31. Nutrient composition by day of winter oat pastures

d P-value

Item, % 0 28 56 84 98 SE Day Diet Day × Diet

DM 17.9 44.9 24.6 32.3 50.7 3.28 .01 .34 .34 OM 86.3 89.0 88.5 91.3 91.2 0.35 .01 .89 .43 NDF 40.8 42.4 45.5 51.3 55.2 0.84 .01 .86 .40 ADF 19.3 19.4 23.6 27.2 29.4 0.45 .01 .28 .63 CP 22.7 17.5 15.9 10.1 8.4 0.93 .01 .99 .79

Both dietary treatments had lower ADG in the first period relative to the last period. This

is contrary to expectations that ADG would decline as crude protein declines concurrent

to increased neutral and acid detergent fiber levels. However, previous findings have

indicated similar responses due to an initial period of reduced forage DMI associated

with inability to process high levels of soluble N (Chalupa et al., 1964; Phillips, 1986;

Phillips and Horn, 2008). Climatic data collected with exception of wind are provided in

Table 32.

Table 32. Weather data expressed as means within collection period

d

Item 1 – 28 29 – 56 57 – 84 85 - 98

Min temp, ºC 2.8 7.2 13.3 15.9 Max temp, ºC 15.0 21.1 25.6 29.5 Humidity, % 65.3 63.9 63.8 59.6 Precipitation, cm1 7.9 0.8 1.8 0.0 1Precipitation expressed as total accumulation within collection period.

Conclusion

Response to an energy supplement containing monensin did not significantly

influence final BW or cumulative ADG of steers grazing small grains. At the only

117

significant observation, supplement void of ionophore resulted in increased gains. These

results are not supported in a consistent manner by previous study and are attributed here

to an inadequate level of monensin-containing supplement intake. However, modeled

forage intake to meet gains did indicate an increased energy effect by which forage level

necessary to achieve results in the absence of supplement was reduced. Use of

metaphylaxis in steers at initiation of the trial improved ADG for the first 28 days of

grazing relative to untreated steers. Use of a single dose implant was effective at

increasing weight gain for the entire 98 day grazing period. Combinations of the

technologies did not increase performance.

118

LITERATURE CITED Babcock, A. H., B. J. White, S. S. Dritz, D. U. Thomson, and D. G. Renter. 2009.

Feedlot health and performance effects associated with the timing of respiratory

disease treatment. J. Anim. Sci. 87:314-327.

Bailey, D. W., and D. Jensen. 2008. Method of supplementation may affect cattle

grazing patterns. J. Range Manage. 61:131-135.

Barker, D. J., P. J. May, and W. M. Jones. 1988. Controlling the intake of grain

supplements by cattle using urea/superphosphate. Pages 146-149 in Proc.

Australian Society of Animal Production, Sydney, Australia.

Barrentine, B. F., and B. G. Ruffin. 1958. Salt and gypsum as regulators of cottonseed

meal intake. Agric. Exp. Sta. Information Sheet 587:1. Mississippi State Univ.,

Starkeville.

Beauchemin, K. A., and S. M. McGinn. 2006. Methane emissions from beef cattle:

Effects of fumaric acid, essential oil, and canola oil. J. Anim. Sci. 84:1489–1496.

Beck, P. A. 1993. Development of a self-limited monensin-containing energy

supplement for growing cattle on wheat pasture. M.S. Thesis, Oklahoma State

Univ., Stillwater.

Behnke, K. C. 2007. Feed manufacturing considerations for using DDGs in poultry and

livestock diets. In: Proc. 5th Mid-Atlantic Nutrition Conference, College Park,

MD.

119

Behnke, K.C., and R. S. Beyer. 2002. Effect of feed processing on broiler performance.

In: Proc. 8th International Seminar on Poultry Production and Pathology.

Santiago, Chile.

Belyea, R. L., B. J. Steevens, R. J. Restrepo, and A. P. Clubb. 1989. Variation in

composition of by-product feeds. J. Dairy Sci. 72:2339.

Belyea, R. L., K. D. Rausch, and M. E. Tumbleson. 2004. Composition of corn and

distillers’ dried grains with solubles from dry grind ethanol processing.

Bioresour. Technol. 94:293–298.

Bowman, J.G.P, and B. F. Sowell. 1997. Delivery method and supplement consumption

by grazing ruminants: a review. J. Anim. Sci. 75:543-550.

Burrin, D. G., R. A. Stock, and R. A. Britton. 1988. Monensin level during grain

adaptation and finishing performance in cattle. J. Anim. Sci. 66:513.

Carro, M. D., M. J. Ranilla, F. J. Giraldez, and A. R. Mantecon. 2006. Effects of malate

on diet digestibility, microbial protein synthesis, plasma metabolites, and

performance of growing lambs fed a high-concentrate diet. J. Anim. Sci. 84:405–

410.

Catsaounis, N., D. Zygoyiannis, S. Kyriaks, C. Tsaltas. 1980. Deltion tes Hellenikes

Kteniatrikes Hetereias (Bulletin of the Hellenic Veterinary Medical Society).

31:253-258.

Chalupa, W., J. L. Evans, and M. C. Stillions. 1964. Metabolic aspects of urea utilization

by ruminant animals. J. Nutr. 84:77–82.

120

Chase, C. C. and C. A. Hibberd. 1987. Utilization of low-quality native grass hay by

beef cows fed increasing quantities of corn grain. J. Anim. Sci. 65:557-566.

DelCurto, T. R., R. C. Cochran, L. R. Corah, A. A. Beharka, E. S. Vanzant, and D. E.

Johnson. 1990. Supplementation of dormant tallgrass-prairie forage: II.

Performance and forage utilization characteristics in grazing beef cattle receiving

supplements of different protein concentrations. J. Anim. Sci. 68: 532-542.

Dixon, R. M., A. White, P. Fry, and J. C. Petherick. 2003. Effects of supplement type

and previous experience on variability in intake of supplements by heifers. Aust.

J. Agric. Res. 54:529-540.

Dove, H., and M. Freer. 1986. The use of tritiated gypsum for estimating individual feed

intakes of pelleted or unpelleted supplement by lambs fed individually or in

groups. Aust. J. Exp. Agric. 26:19-22.

Ducker, M. J., P. T. Kendall, R. G. Hemingway, and T. H. McClelland. 1981. An

evaluation of feedblocks as a means of providing supplementary nutrients to

ewes grazing upland/hill pastures. Anim. Prod. 33:51.

Edwards, A. 1996. Respiratory diseases of feedlot cattle in central USA. Bov. Pract.

30:5-7.

Foley, P. A., D. A. Kenny, J. J. Callan, T.M. Boland, and F. P. O’Mara. 2009. Effect of

DL-malic acid supplementation on feed intake, methane emission, and rumen

fermentation in beef cattle. J. Anim. Sci. 87:1048-1057.

121

Foot, J. Z., A. J. F. Russel, T. J. Maxwell, and P. Morris. 1973. Variation in intake

among group-fed pregnant Scottish Blackface ewes given restricted amount of

food. Anim. Prod. 17:169.

Galyean, M. L., S. A. Gunter, and K. J. Malcom-Callis. 1995. Effects of arrival

medication with tilmicosin phosphate on health and performance of newly

received beef cattle. J. Anim. Sci. 73:1219–1226.

Garossino, K. C., B. J. Ralston, T. A. McAllister, and M. E. Olson. 2003. Measuring

individual free-choice protein supplement consumption by wintering beef cattle.

Can. J. Anim. Sci. 83 (1):21-27.

Griffin, W. A., V. R. Bermer, T. J. Klopfenstein, L. A. Stalker, L. W. Lomas, J. L.

Moyer, and G. E. Erickson. 2009. Summary of grazing trials using dried

distillers’ grains supplementation. Nebr. Beef Rep. (Lincoln) MP92:37.

Horn, G. W., M. D. Cravey, F. T. McCollum, C. A. Strasia, E. G. Krenzer, Jr., and P. L.

Claypool. 1995. Influence of high-starch vs high-fiber energy supplements on

performance of stocker cattle grazing wheat pasture and subsequent feedlot

performance. J. Anim. Sci. 73:45-54.

Horn, G. W., T. L. Mader, S. L. Armbruster and R. R. Frahm. 1981. Effect of monensin

on ruminal fermentation, forage intake and weight gains of wheat pasture stocker

cattle. J. Anim. Sci. 52:447.

Huston, F. E., H. Lippke, T. D. A. Forbes, J. W. Holloway, and R. V. Machen. 1999.

Effects of supplemental feeding interval on adult cows in western Texas. J.

Anim. Sci. 77:3057-3067.

122

Jensen, J. E. 1979. Restricting intake of energy supplements fed to yearling steers

grazing irrigated pasture. M.S. thesis. Univ. of Nebraska, North Platte.

Judkins, M. B., L. J. Krysl, J. D. Wallace, M. L. Galyean, K. D. Jones, and E. E. Parker.

1985. Intake and diet selection by protein supplemented grazing steers. J. Range

Manage. 38:210-382.

Kendall, P. T., R. G. Hemingway, and M. J. Ducker. 1980. Variation in probable intake

of ewes given concentrates with varying trough-space allowance or self-help

feedblocks. Proc. Nutr. Soc. 30:16A.

Klopfenstein, T. J., L. Lomas, D. Blasi, D. C. Adams, W. H. Schacht, S. E. Morris, K.

H. Gustad, M. A. Greenquist, R. N. Funston, J. C. MacDonald, and M. Epp.

2007. Summary analysis of grazing yearling response to distillers’ grains.

Nebraska Beef Cattle Rep. MP90:10.

Köster, H. H., R. C. Cochran, E. C. Titgemeyer, E. S. Vanzant, T. G. Nagaraja, K. K.

Kreikemeier, and G. St. Jean. 1997. Effect of increasing proportion of

supplemental nitrogen from urea on intake and utilization of low-quality

tallgrassprairie forage by beef steers. J. Anim. Sci. 75:1393-1399.

Kreikemeier, K., G. Stokka, and T. Marston. 1996. Influence of delayed processing and

mass medication with either chlortetracycline or tilmicosin phosphate on health

and growth of highly stressed calves. Kansas State Univ. Southwest Res. Ext.

Cent. Rep. Kansas State Univ., Manhattan.

123

Kuhl, G. L. 1997. Stocker cattle responses to implants. Symposium: Impact of implants

on performance and carcass value of beef cattle. Okla. Agric. Exp. Sta. P-957:51-

62.

Kung, L., Jr., J. T. Huber, J. D. Krummrey, L. Allison, and R. M. Cook. 1982. Influence

of adding malic acid to dairy cattle rations on milk production, rumen volatile

acids, digestibility, and nitrogen utilization. J. Dairy Sci. 65:1170-1174.

Kunkle, W. E., J. T. Johns, M. H. Poore, and D. B. Herd. 2000. Designing

supplementation programs for beef cattle fed forage-based diets. Proc. Am.

Anim. Sci., 1999. Available at: http://www.asas.org/jas/symposia/proceedings/

0912.pdf. Accessed July 22, 2011.

Lane, M. A., M. H. Ralphs, J. D. Olsen, F. D. Provenza, and J. A. Pfister. 1990.

Conditioned taste aversion: potential for reducing cattle losses to larkspur. J.

Range Manage. 43:127-131.

Lemenager, R. P., F. N. Owens, K. S. Lusby and Robert Totusek. 1978. Monensin,

forage intake and lactation of range beef cows. J. Anim. Sci. 47:247

Leupp, J. L., G. P. Lardy, K. K. Karges, M. L. Gibson, and J.S. Canton. 2009. Effects of

increasing level of corn distillers’ dried grains with solubles on intake, digestion,

and ruminal fermentation in steers fed 70% concentrate diets. J. Anim. Sci.

87:2906–2912.

Lobato, J.F.P., and G. R. Pearce. 1980. Responses to molasses-urea blocks of grazing

sheep and sheep in yards. 1980. Aust. J. Exp. Agric. Anim. Husb. 20:417-421.

124

Lobato, J.F.P., G. R. Pearce, and R. G. Beilharz. 1980. Effect of early familiarization

with dietary supplements on the subsequent ingestion of molasses-urea blocks by

sheep. App. Anim. Eth. 6:149-161.

Lodge, S. L., R. A. Stock, T. J. Klopfenstein, D. H. Shain, and D.W. Herold. 1997.

Evaluation of corn and sorghum distillers’ byproducts. J. Anim. Sci. 75:37–43.

Loy, T. W., J. C. MacDonald, T. J. Klopfenstein, and G. E. Erickson. 2007. Effect of

distillers’ grains or corn supplementation frequency on forage intake and

digestibility. J. Anim. Sci. 85:2625–2630.

MacDonald, J.C., and T.J. Klopfenstein. 2004. Dried distillers’ grains as a grazed forage

supplement. Nebr. Beef Cattle Rep. MP 80-A: 25-27.

Martin, S. A., M. N. Streeter, D. J. Nisbet, G. M. Hill, and S. E. Williams. 1999. Effects

of dl-malate on ruminal metabolism and performance of cattle fed a high-

concentrate diet. J. Anim. Sci. 77:1008–1015.

McCollum, F. T. III, and G. W. Horn. 1990. Protein supplementation of grazing

livestock: A review. Prof. Anim. Sci. 6:1–16.

McCollum, F. T. III. 1996. Grazing stocker cattle on small grains. Page 37 in Proc.

Southwest Beef Management Symposium, Tucumcari, New Mexico.

McCourt, A. R., T. Yan, S. Mayne, and J. Wallace. 2008. Effect of dietary inclusion of

encapsulated fumaric acid on methane production from grazing dairy cows. Page

64 in Proc. Br. Soc. Anim. Sci. Annu. Conf., Scarborough, UK. Br. Soc. Anim.

Sci., Midlothian, Scotland.

125

McGinn, S. M., K. A. Beauchemin, T. Coates, and D. Colombatto. 2004. Methane

emissions from beef cattle: Effects of monensin, sunflower oil, enzymes, yeast,

and furmaric acid. J. Anim. Sci. 82:3346–3356.

McMurphy, C. P., E. D. Sharman, D. A. Cox, G. W. Horn, and D. L. Lalman. 2010.

Effects of implant type and protein source on growth of steers grazing summer

pasture. Proc. West. Sect. Am. Soc. Anim. Sci. 61:100-105.

Meyer, J. H., W. C. Weir, N. R. Ittner, and J. D. Smith. 1955. The influence of high

sodium chloride intakes by fattening sheep and cattle. J. Anim. Sci. 14:412-418.

Molano, G., T. W. Knight, and H. Clark. 2008. Fumaric acid supplements have no effect

on methane emissions per unit of feed intake in wether lambs. Aust. J. Exp.

Agric. Sci. 48:165–168.

Montano, M. F., W. Chai, T. E. Zinn-Ware, and R. A. Zinn. 1999.Influence of malic

acid supplementation on ruminal pH, lactic acid utilization, and digestive

function in steers fed high concentrate finishing diets. J. Anim. Sci. 77:780–784.

Morris, S. E., J. C. MacDonald, D. C. Adams, T. J. Klopfenstein, R. L. Davis, and J. R.

Teichert. 2006. Effects of supplanting dried distillers’ grains to steers grazing

summer sandhill range. Nebr. Beef Cattle Rep. MP 88A:30–32.

Morris, S. E., T. J. Klopfenstein, D. C. Adams, G. E. Erickson, and K. J. Vander Pol.

2005. The effects of dried distillers’ grains on heifers consuming low or high-

quality forage. Nebraska Beef Cattle Report. MP 83-A:18–20.

126

Mulholland, J. G., and J. B. Coombe. 1979. Supplementation of sheep grazing wheat

stubble with urea, molasses and minerals: quality of diet, intake of supplements

and animal response. Aust. J. Exp. Agric. Anim. Husb. 19:23-31.

Muller, R. D., E. L. Potter, M. I. Wray, L. F. Richardson, and H. P. Grueter. 1986.

Administration of monensin in self-fed (salt limiting) dry supplements or on an

alternate-day feeding schedule. J. Anim. Sci. 62:593-600.

Newbold, C. J., S. Lopez, N. Nelson, J. O. Ouda, R. J. Wallace, and A. R. Moss. 2005.

Propionate precursors and other metabolic intermediates as possible alternative

electron acceptors to methanogenesis in ruminal fermentation in vitro. Br. J.

Nutr. 94:27–35.

Nickell, J. S. and B. J. White. 2010. Metaphylactic antimicrobial therapy for bovine

respiratory disease in stocker and feedlot cattle. Veterinary Clinics of North

America: Food Animal Practice. 26:285-301.

NRC. 1996. Nutrient Requirements of Beef Cattle. 7th rev. ed. Natl. Acad. Press,

Washington, DC.

Oba, M., and M. S. Allen. 2003. Intraruminal infusion of propionate alters feeding

behavior and decreases energy intake of lactating dairy cows. J. Nutr. 133:1094–

1099.

Paisley, S. I., and G. W. Horn. 1996. Effects of monensin on intake of a self-limited

energy supplement for growing steers grazing winter wheat pasture. J. Anim. Sci.

74(Suppl. 1):37.

127

Phillips, W. A. 1986. Adaptation of stocker calves to non-protein nitrogen diets as a

result of grazing wheat forage. J. Anim. Sci. 62:464–472.

Phillips, W. A., and G. W. Horn. 2008. Intake and digestion of wheat forage by stocker

calves and lambs. J. Anim. Sci. 86:2424-2429.

Pinchak, W. E., W. D. Worrall, S. P. Caldwell, L. J. Hunt, N. J. Worrall, and M. Conoly.

1996. Interrelationships of forage and steer growth dynamics on wheat pasture. J.

Range Manage. 49:126–130.

Potter, E. L., R. D. Muller, M. I. Wray, L. H. Carroll, and R. M. Meyer. 1986. Effect of

monensin on the performance of cattle on pasture or fed harvested forages in

confinement. J. Anim. Sci. 62:583-592.

Provenza, F. D. 1995. Postingestive feedback as an elemental determinant of food

preference and intake in ruminants. J. Range Manage. 48:2.

Provenza, F. D. 1996a. Acquired aversions as the basis for varied diets of ruminants

foraging on rangelands. J. Anim. Sci. 74:2010.

Provenza, F. D. 1996b. A functional explanation for palatability. In N.E. West (Ed.)

Proc. Fifth Int. Rangeland Cong. Soc. Range Manage., Denver, CO (In press).

Provenza, F. D., C. B. Scott, T. S. Phy, and J. J. Lynch. 1996. Preferences of sheep for

foods varying in flavors and nutrients. J. Anim. Sci. 74:2355–2361.

Redmon, L. A., F. T. McCollum III, G. W. Horn, M. D. Cravey, S. A. Gunter, P. A.

Beck, J. M. Mieres, andR. San Julian. 1995. Forage intake by beef steers grazing

winter wheat with varied herbage allowances. J. Range Manage. 48:198–201.

128

Richardson, L. F., A. P. Raun, E. L. Potter, C. O. Cooley and R. P. Rathmacher. 1976.

Effect of monensin on rumen fermentation in vitro and in vivo. J. Anita. Sci.

43:657.

Rosentater, K. A. 2006. Physical properties of dried distillers’ grains with soluble

(DDGS). In: Proc. American Society of Agricultural and Biological Engineers

Annual International Meeting, Portland, OR.

Sawyer, J. E., and C. P. Mathis. 2001. Supplement delivery systems. Cooperative

Extension Service – New Mexico State University. Circular 571. Available at:

http://www.cahe.nmsu.edu/pubs/-circulars/Cr-571.pdf. Accessed August 15,

2011

Schauer, C. S., D. W. Bohnert, D. C. Ganskopp, C. J. Richards, and S. J. Falck. 2005.

Influence of protein supplementation frequency on cows consuming low quality

forage: Performance, grazing behaviour and variation in supplement intake. J.

Anim. Sci. 83:1715–1725.

Schauer, C. S., G. P. Lardy, W. D. Slanger, M. L. Bauer, and K. K. Sedivec. 2004. Self-

limiting supplements fed to cattle grazing native mixed-grass prairie in the

northern Great Plains. J. Anim. Sci. 82:298-306.

Schelling, G. T. 1984. Monensin mode of action in the rumen. J. Anim. Sci. 58:1518–

1527.

Selk, G. E., R. R. Reuter, and G. L. Kuhl. 2006. Using growth-promoting implants in

stocker cattle. Veterinary Clinics of North America: Food Animal Practice.

22:435-449.

129

Spiehs, M. J., M. H. Whitney, and G. C. Shurson. 2002. Nutrient data for distiller’s dried

grains with solubles produced from new ethanol plants in Minnesota and South

Dakota. J. Anim. Sci. 80:2639–2645.

Step, D. L., T. Engelken, C. Romano, B. Holland, C. Krehbiel, J. C. Johnson, W. L.

Bryson, C. M. Tucker, and E. J. Robb. 2007. Evaluation of three antimicrobial

regimens used as metaphylaxis in stocker calves at high risk of developing

bovine respiratory disease. Vet. Ther. 8:136-147.

Stock, R., T. Klopfenstein and D. Shain. 1995. Feed intake variation. Proc. Symp: Feed

Intake by Feedlot Cattle. Okla. State Univ., Stillwater. P-942:56–59.

Stock, R. A., S. B. Laudert, W. W. Stroup, E. M. Larson, J. C. Parrott, and R. A. Britton.

1995. Effect of monensin and monensin tylosin combination of feed intake

variation of feedlot steers. J. Anim. Sci. 73:39-44.

Tait, R. M., and L. J. Fisher. 1996. Variability in individual animal’s intake of minerals

offered free-choice to grazing ruminants. Anim. Feed Sci. and Tech. 62:69-76.

Taylor, N., P. G. Hatfield, B. F. Sowell, J.G.P. Bowman, J. S. Drouillard, and D. V.

Dhuyvetter. 2002. Pellet and block supplements for grazing ewes. Anim. Feed

Sci. and Tech. 96:193-201.

Utley, P. R., G. L. Newton, R. J. Ritter III and W. C. McCormick. 1976. Effects of

feeding monensin in combination with zeranol and testosterone estradiol

implants for growing and finishing heifers. J. Anim. Sci. 42:754.

130

Wallace, L. R., and O. F. Parker. 1966. Comparison of three systems of feeding silage

after calving. Pages 148–158 in Proc. Ruakura Farmers’ Conference, Ruakura,

New Zealand.

Wallace, R. J., T. A. Wood, A. Rowe, J. Price, D. R. Yanez, S.P. Williams, and C. J.

Newbold. 2006. Encapsulated fumaric acid as a means of decreasing ruminal

methane emissions. Int. Congr. Ser. 1293:148–151.

Waller, J., T. Klopfenstein, and M. Poos. 1980. Distillers’ feeds as protein sources for

growing ruminants. J. Anim. Sci. 51:1154.

Wang, C., Q. Liu, W. Z. Yang, Q. Dong, X. M. Yang, D. C. He, K. H. Dong, and Y. X.

Huang. 2009. Effects of malic acid on feed intake, milk yield, milk components

and metabolites in early lactation Holstein dairy cows. Livest. Prod. Sci.

124:182-188

Waterman, R. C., J. E. Sawyer, C. P. Mathis, D. E. Hawkins, G. B. Donart, and M. K.

Petersen. 2006. Effects of supplements that contain increasing amounts of

metabolizable protein with or without Ca-propionate salt on postpartum interval

and nutrient partitioning in young beef cows. J. Anim. Sci. 84:433–446.

Wileman, B. W., D. U. Thomson, C. D. Reinhardt, and D. G. Renter. 2009. Analysis of

modern technologies commonly used in beef cattle production: Conventional

beef production versus nonconventional production using meta-analysis. J. Anim

Sci. 87:3418-3426.

Wise, M. B., E. R. Barrick, and T. N. Blumer. 1965. Finishing steers with grain on

pasture. Agric. Exp. Sta. Bull. 425. North Carolina Stat

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